datastore/CHANGELOG.md

Watch all release presentations and videos at ClickHouse Theater and YouTube Playlist.

Table of Contents

ClickHouse release v26.6, 2026-06-25
ClickHouse release v26.5, 2026-05-21
ClickHouse release v26.4, 2026-04-30
ClickHouse release v26.3 LTS, 2026-03-26
ClickHouse release v26.2, 2026-02-26
ClickHouse release v26.1, 2026-01-29
Changelog for 2025
Changelog for 2024
Changelog for 2023
Changelog for 2022
Changelog for 2021
Changelog for 2020
Changelog for 2019
Changelog for 2018
Changelog for 2017

2026 Changelog

ClickHouse release 26.6, 2026-06-25. Presentation, Video

Backward Incompatible Change

• The change removes allow_experimental_query_deduplication feature. The feature was experimental for a long time, has no tests and not going to be supported (initial tests were unstable and has been removed in #49579). #99398 (Igor Nikonov).
• The XRay-based SYSTEM INSTRUMENT feature now uses arguments instead of parameters: the system.instrumentation.parameters column was renamed to arguments, and the SYSTEM INSTRUMENT ADD ... HANDLER PARAMETERS ... syntax was renamed to SYSTEM INSTRUMENT ADD ... HANDLER ARGUMENTS .... Queries or automation that use the old column or syntax must be updated to use the new names; the old names are no longer supported. #103854 (Pablo Marcos).
• The setting show_data_lake_catalogs_in_system_tables has been renamed to show_remote_databases_in_system_tables and broadened: when its value is 0 (the default), MySQL and PostgreSQL databases are also hidden from system.tables, system.columns, and system.completions, in addition to data lake catalogs. The old setting name is kept as an alias. #104416 (Pablo Marcos).
• The default x86 build now targets x86-64-v3 (AVX2) instead of x86-64-v2 (SSE4.2). This requires a CPU with AVX2 support (Intel Haswell or later, AMD Excavator or later). If your CPU does not support AVX2, use the amd64compat build which targets plain x86-64. #105019 (Raúl Marín).
• Reject nested Dynamic/Variant in min/max aggregates and minmax indexes. Previously only top-level Dynamic/Variant were checked. Closes #104747. #105468 (Pavel Kruglov).
• icebergHash and icebergBucket now reject Int128, UInt128, Int256, UInt256, and Decimal256 arguments with an explicit error. Previously they silently truncated wider values and produced colliding hashes. The Iceberg spec only defines hashing for 32/64-bit integers and decimals with precision up to 38; cast to Int64 or Decimal128 to keep the previous behaviour for values that fit. #105866 (Raúl Marín).
• Added granular control over query echoing in the CLI. The --echo option now accepts an optional boolean value and works in both interactive and batch mode. New options --echo-formatted and --echo-query-id control whether echoed queries are formatted and whether the query_id is printed, respectively. The --hilite/--highlight option now also controls highlighting of echoed queries. As a side effect, --echo is now a boolean-value option, so a positional query directly after a bare --echo is treated as its value; use --echo --query "..." or --echo=false instead. #106191 (Alexey Milovidov).
• Removed the experimental KQL (Kusto) functions array_sort_asc and array_sort_desc, and their SQL backends kql_array_sort_asc and kql_array_sort_desc. These functions were experimental, implemented with low quality, and the source of correctness and parser bugs. Queries using these names now return UNKNOWN_FUNCTION. #108101 (Groene AI).
• ALTER TABLE ... REPLACE PARTITION ... FROM ... no longer silently drops the destination partition's data when the source table has no parts in the requested partition. Previously such a request removed the destination partition and wrote nothing in its place — a data-loss footgun. It is now rejected with BAD_ARGUMENTS by default. To restore the previous silent-clear behavior, set the new setting allow_replace_partition_from_empty_source = 1, or set compatibility to 26.5 or lower; to explicitly drop destination data, use ALTER TABLE ... DROP PARTITION. #104939 (Groene AI).
• The default of the server setting insert_deduplication_version changes from compatible_double_hashes to new_unified_hash. Insert deduplication now works on the whole inserted block (per insert) rather than per part/partition: a retry of the same insert is still deduplicated, but two different inserts that produce an identical part are no longer cross-deduplicated, and reordered inserts of the same rows are no longer deduplicated. Set insert_deduplication_version = compatible_double_hashes to restore the previous behavior. Instances upgrading directly from a release that defaulted to old_separate_hashes should first run with compatible_double_hashes until the longest relevant deduplication window has elapsed before relying on new_unified_hash. #107886 (Sema Checherinda).

New Feature

• Added support for continuous queries over MergeTree tables, implemented via a series of snapshot reads. This is a first step toward general support for streaming queries. #105114 (Mikhail Artemenko).
• Added hypothetical (what-if) skip indexes. Use CREATE HYPOTHETICAL INDEX ... ON t (expr) TYPE ... to define a session-scoped virtual skip index, then EXPLAIN WHATIF SELECT ... to estimate its skip ratio and cost without materializing it. Defined indexes are visible in the new system.hypothetical_indexes table. #104608 (Yarik Briukhovetskyi).
• Add an embedded /schema web UI to clickhouse-server that visualizes the dependency graph between tables, materialized views, refreshable materialized views, dictionaries, distributed tables and views. #105276 (Nikita Mikhaylov).
• Added the PNG output format support, allowing query output results to be directly rendered as PNG images. #74691 (Maksim Dergousov).
• Added detection of the AI coding agent (Claude Code, Cursor, Codex, Gemini CLI, Goose, etc.) that invoked clickhouse-client or clickhouse-local, based on environment variables. The detected agent is reported in the new client_agent column of system.query_log, system.query_thread_log and system.processes. #106619 (Alexey Milovidov).
• Added a new system table system.documentation that collects the embedded reference documentation of the uniform components of the system (functions, table engines, data types, settings, formats, and others) into a single table, with the documentation rendered as Markdown. #107463 (Alexey Milovidov).
• Add the GeoJSON input format for reading GeoJSON FeatureCollection documents, producing one row per feature with id (String), geometry (Geometry), and properties (Nullable(JSON)) columns. Point, LineString, MultiLineString, Polygon, and MultiPolygon geometries are read into ClickHouse's native Geometry type. GeometryCollection and MultiPoint, which the Geometry type cannot represent, raise an exception by default, or can be stored as NULL via the input_format_geojson_unsupported_geometry_handling setting. Contributes to #91533. #98124 (Mark Needham).
• Added functions for serving Mapbox Vector Tiles directly from SQL: MVTEncodeGeom projects a geometry into the pixel space of a slippy-map tile and clips it, MVTEncode aggregates the projected geometries of a group into the binary bytes of a single-layer tile, and MVTBoundingBox / MVTBoundingBoxMercator return the bounding box of a tile for restricting rows to it. Point, line and polygon geometry is supported. Also available under the PostGIS aliases ST_AsMVTGeom and ST_AsMVT. #106107 (Saarthak Gupta).
• clickhouse-local now supports SYSTEM START LISTEN and SYSTEM STOP LISTEN queries, allowing it to be transformed into a server accepting TCP and HTTP connections. #101143 (Alexey Milovidov).
• Added an interactive help command to clickhouse-client and clickhouse-local. Typing help <name> (also /help, man, /man) shows the documentation of a function, table engine, data type, format, setting, or other component, rendered from Markdown in the terminal with syntax-highlighted SQL. When the word is ambiguous all matches are shown, and when it is not found, similar names are suggested. #108042 (Alexey Milovidov).
• Support writing into Azure Data Lake Storage Gen2. #105406 (Konstantin Vedernikov).
• Adding RowBinaryWithNamesAndTypesAndDefaults format to get better support for schema evolution. #105736 (Mark Zitnik).
• Implement ADD ENUM VALUES in ALTER TABLE queries to simplify appending new values to an existing Enum type without the need to specify all current Enum values again. #93830 (Ilya Golshtein).
• Refreshable materialized view now supports REFRESH DEPENDS ON to trigger refreshes on another RMV's refreshes instead of time-based schedule. (REFRESH EVERY ... DEPENDS ON already existed, but couldn't be used reliably for this use case.) See CREATE MATERIALIZED VIEW documentation. #104440 (Michael Kolupaev).
• Add support for selecting columns by name pattern with * LIKE '<pattern>' and * ILIKE '<pattern>', including qualified forms such as table.* LIKE '<pattern>' and table.* ILIKE '<pattern>'. LIKE matches column names case-sensitively, ILIKE case-insensitively. #104569 (Yue Ni).
• Added ESCAPE syntax that defines a custom escape character in a LIKE pattern, allowing you to treat % and _ as literal characters instead of wildcards. #99774 (Ilya Yatsishin).
• Add materialize_projections_on_insert and materialize_projections_on_merge MergeTree table settings. When materialize_projections_on_insert = 0, INSERTs skip building projection parts, which improves insert throughput for tables with many projections. When materialize_projections_on_merge = 1, a merge rebuilds a projection that is missing from all of its source parts, so projections can be built during merges instead of on insert. Merges still combine only parts that share the same set of projections. #100993 (Christoph Wurm).
• Add a new immutable MergeTree setting allow_tuple_element_aggregation, disabled by default. When enabled, SummingMergeTree, AggregatingMergeTree and CoalescingMergeTree recursively flatten Tuple columns and aggregate each leaf element independently during merges, exactly as if it were a top-level column — SummingMergeTree sums it, AggregatingMergeTree merges its aggregate-function state, and CoalescingMergeTree keeps its last non-NULL value. The setting must be specified at table creation time and is silently ignored by engines that do not support it. #98039 (johnjing).
• New functions quantizeBFloat16ToInt8 and dequantizeInt8ToBFloat16: a scalar codec that compresses embedding components to 8-bit using a 256-level Gaussian Lloyd-Max quantizer, from which Int4/Int2/binary codes can be extracted by bit-truncation. #108102 (Alexey Milovidov).
• Add functions arrayTopK and arrayBottomK: - arrayTopK(k, array) returns the K largest elements in descending order - arrayBottomK(k, array) returns the K smallest elements in ascending order. #104563 (Vitaly Baranov).
• Added a new system table system.iceberg_files exposing per-file metadata for Iceberg tables, with one row per data or delete file in each table's current snapshot. This closes #98777. #104415 (Asya Shneerson).
• Added system.constraints table that provides information about all CHECK and ASSUME constraints across all tables, including constraint name, type, and expression. #105337 (Pedro Ferreira).
• Added a new system.dictionary_layouts table that lists the available dictionary layouts together with embedded documentation (description, syntax, examples, introduced_in, related). #106182 (Alexey Milovidov).
• Added a new system.dictionary_sources table that lists the available dictionary sources together with embedded documentation (description, syntax, examples, introduced_in, related). #106184 (Alexey Milovidov).
• Added a new system.data_skipping_index_types table that lists the available data skipping index types together with embedded documentation (description, syntax, examples, introduced_in, related). #106186 (Alexey Milovidov).
• Added a new system.disk_types table that lists the available disk types together with embedded documentation (description, syntax, examples, introduced_in, related). #106187 (Alexey Milovidov).
• Implemented SYSTEM RESTART DISK <name>: it now reloads a disk's in-memory metadata and re-scans the data parts of readonly-replica tables located on it. This lets a readonly replica of a table on shared plain_rewritable storage observe data written by another server on demand, without waiting for refresh_parts_interval or restarting the server. #106645 (Jordi Villar).
• PostgreSQL-style expr OP SOME(array) / expr OP ALL(array) (non-subquery right-hand side) is now supported and rewritten to has / NOT has for =/<>, or to arrayExists / arrayAll lambdas for other comparison operators. ANY is not accepted for the array form because any is also an aggregate function; use SOME instead. The subquery form of ANY/SOME/ALL continues to be lowered to IN / NOT IN. #105129 (Alexey Milovidov).
• Added two new load_balancing strategies, hostname_longest_common_prefix and hostname_longest_common_suffix, which prefer the replica whose hostname shares the longest common prefix (respectively, suffix) with the initiator's hostname. They are useful when the data center is encoded as a prefix or suffix of hostnames whose numeric segments have variable length, where the existing nearest_hostname and hostname_levenshtein_distance strategies pick the wrong replica. #107360 (Denny [DBA at Innervate]).
• Added TLS client certificate information (subjects, serial number, issuer, and validity period) to the system.session_log table to improve observability of certificate-based authentication. #107679 (Alexey Milovidov).
• Add an optional external_id credential for S3 role-based access. #106941 (Elian Gidoni).
• Added a new S3Queue setting after_processing_move_preserve_path. When enabled together with after_processing='move' and after_processing_move_prefix, processed objects are moved while preserving their full source path under the destination prefix instead of being flattened to just the file name. #105354 (Asya Shneerson).
• Add message_queue_disable_insertion server setting to disable insertion from message queue engines (Kafka, RabbitMQ, NATS) into attached materialized views. Useful for read-only replica scenarios. #104911 (JIaQi Tang).
• Added LOCALTIME and LOCALTIMESTAMP (SQL-standard / PostgreSQL syntax). LOCALTIMESTAMP is an alias for now() (returns DateTime); LOCALTIME returns the current time of day as a Time value. #106139 (Thomas Cabral).
• Added date_part('unit', expr) as syntactic sugar for EXTRACT(unit FROM expr). Standard interval kinds and the PostgreSQL extras (epoch, dow, doy, isodow, isoyear, century, decade, millennium) are all supported. #105127 (Alexey Milovidov).
• PostgreSQL-compatible EXTRACT(TIMEZONE_HOUR FROM dt) and EXTRACT(TIMEZONE_MINUTE FROM dt) for the hour and minute parts of a timezone offset, and EXTRACT(<unit> FROM INTERVAL n <unit>) / date_part('<unit>', INTERVAL n <unit>) for extracting the value out of an interval. #106227 (Vinayak Joshi).
• Added min_by and max_by aggregate aliases for argMin and argMax. #105712 (Joey Yu). These aliases are stupid, real engineers use the original ClickHouse names.
• Added REGEXP_SUBSTR as a case-insensitive alias of regexpExtract for Oracle/MySQL/Snowflake compatibility. #105122 (Alexey Milovidov).
• Added SESSION_USER as a case-insensitive alias of currentUser() for PostgreSQL / SQL-standard compatibility. #106081 (Takumi Hara).
• Support a trailing NULL / NOT NULL modifier in ALTER TABLE ... ADD/MODIFY COLUMN, mirroring CREATE TABLE. #106150 (Takumi Hara).
• You can now use h3PolygonToCellsWithContainment function from h3 to use their new algorithm which supports center-based, fully-contained, and overlapping containment modes. #104455 (Youssef Kadry).
• Adds IPV4_PREFIX_BITS and IPV6_PREFIX_BITS flags when Keying done by IP_ADDRESS or FORWARDED_IP_ADDRESS. #89270 (Aditya Chopra).
• formatReadableTimeDelta now accepts an INTERVAL expression of type other than Month and Year as input. #64315 (Francisco J. Jurado Moreno).
• User can now specify an optional precision argument to the formatReadableSize, formatReadableDecimalSize and formatReadableQuantity functions, controlling the number of digits after the decimal point. Default is 2, preserving the prior behavior. #104648 (Antonio Filipovic).
• Add output_format_float_precision setting to control the number of decimal digits in floating-point text output. #99721 (phulv94).
• Added a setting output_format_always_write_decimal_point_in_float_and_decimal to always print a decimal point for floating-point and Decimal numbers in text formats, even when the value is a whole number. For example, output 1. instead of 1. Disabled by default. #62614 (Ilya Yatsishin).
• Add support for new HTTP handler configuration elements <url_prefix> and <full_url_prefix> (match all paths under a base path, useful e.g. for Prometheus handlers), as well as <url_regexp>, <full_url_regexp>, and <headers_regexp>. The old <url>regex:...</url> form is now obsolete. #107492 (Vitaly Baranov).
• Support basic statistics, a compact per-column statistic that stores numeric min/max, average string length, and NULL counts where applicable. #106048 (Han Fei).
• Support TTL nodes in ClickHouse Keeper, opt-in via the create_ttl feature flag. #100397 (Konstantin Vedernikov).
• Introduce a memory reservation feature for workloads. See the workload scheduling documentation. #82414 (Sergei Trifonov).

Experimental Feature

• Multi-stage distributed query execution: the planner splits the query plan into stages connected by scatter / broadcast / gather / shuffle exchanges and dispatches the plan fragments to worker nodes. The data between stages is streamed via TCP or passed via temporary files in shared object storage, the path supports distributed shuffle and broadcast hash joins, shuffle aggregation, and distributed sort. The feature is experimental and is disabled by default. #106020 (Alexander Gololobov). The experimental distributed query plan engine (make_distributed_plan) can now use a different task-dispatch and streaming-exchange port per worker, configured per replica in <remote_servers> with stateless_worker_port and streaming_exchange_port. When unset, the previous server-level ports (stateless_worker_client.port and distributed_query.streaming_exchange_port) are used. This makes it possible to run several workers on one host. #107885 (Alexander Gololobov).
• Added the experimental dphyp join reordering algorithm for inner joins as an option for the query_plan_optimize_join_order_algorithm setting, and the query_plan_optimize_join_order_max_searched_plans setting, which bounds the join-order search and falls back to the next algorithm in the chain when the bound is exceeded; set it to 0 to keep the previous unbounded search behavior. #98798 (Alexander Gololobov).
• Add aiEmbed function for using LLM APIs to generate embeddings from within ClickHouse. #102922 (George Larionov).
• Added an experimental Linux OOM canary: a sacrificial child process that the Linux OOM killer targets before the main server process. When enabled with oom_canary_enable, it sheds memory pressure by purging allocator caches, cancelling queries, cancelling merges, and recording an event in system.crash_log. The OOM response requires cgroup v2 memory.events OOM-kill evidence. #101942 (Peng).
• The web terminal interface at /webterminal is now a production feature and is enabled by default. It is controlled by the new enable_webterminal server setting; the former allow_experimental_webterminal setting is deprecated but still honored for backward compatibility. To disable the endpoint, set enable_webterminal to false. #106255 (Alexey Milovidov).
• PromQL HTTP endpoints now support specifying the database and table via URL query parameters (database=, table=, or table=db.table). The previous implicit default.prometheus table fallback is removed: if neither the handler config nor the URL specifies a table, the handler now returns The time series table name is not set. To keep the old behavior, configure <table>default.prometheus</table> or pass table=... in the URL. #107553 (Vitaly Baranov).
• Added support for the PromQL histogram_quantile function in prometheusQuery and prometheusQueryRange table functions. This enables computing quantiles over classic Prometheus histogram buckets identified by the le label. #103477 (Joe Smith).
• Added lazy posting list apply mode for the text index. When enabled via SET allow_experimental_text_index_lazy_apply = 1 and SET text_index_posting_list_apply_mode = 'lazy', posting lists are decoded on demand at packed-block granularity using a cursor-based approach instead of being fully materialized into Roaring Bitmaps, reducing memory usage and CPU time for selective text index queries. #100035 (Peng).
• Added support for the AssemblyScript ABI for WebAssembly UDFs. You can try the AssemblyScript ABI without installing the toolchain locally by using the browser-based playground, which compiles AssemblyScript code and loads the resulting WebAssembly module into local ClickHouse. #104606 (Vladimir Cherkasov).
• Allow for attaching Prometheus handlers on the main HTTP port with an optional prefix. #104975 (James Cunningham).
• Added an experimental MergeTree setting packed_skip_index_max_bytes that bundles small skip-index substreams into a single skp_idx.packed archive per part, reducing inode pressure when many skip indices are defined on a table. The decision is per substream at write time: substreams whose serialized size stays under the threshold go into the archive, anything larger keeps the standalone skp_idx_<name>.idx2 / .mrk2 layout. A single part can mix layouts. Full-text indices are not supported and are always per-file. Default is 0 (packing disabled). #105321 (Raúl Marín).
• Support Buffers serialization for WebAssembly UDFs using ABI BUFFERED_V1, and add webassembly_udf_enable_fuel as a persisted WASM UDF function setting. #105574 (Antonio Andelic).
• Add an experimental use_reader_executor setting (default off) that routes reads through a new pipeline-based ReaderExecutor instead of the legacy chain of read buffers. #106570 (Sema Checherinda). Added observability metrics for the experimental use_reader_executor read path, including a modeled read-cost KPI (ReaderExecutorModeledCostMsPerRequestedMiB). #106968 (Sema Checherinda). Introduced the ChainedBuffers buffer behind the experimental use_reader_executor read path, with a ReaderExecutorChainedBufferBytes metric. #107210 (Sema Checherinda).
• Descending sort order in MergeTree sorting keys (e.g. ORDER BY (time DESC, key)) is now always supported and no longer requires the experimental setting allow_experimental_reverse_key, which became obsolete. #106440 (Nikita Mikhaylov).
• Nullable(Tuple(...)) is now Beta. Disabled by default, set enable_nullable_tuple_type = 1 to use it. #107754 (Nihal Z. Miaji).

Performance Improvement

• Various changes to Keeper that make it around 2x faster overall (better batching, pipelining messages to leader, pipelining log appends). #101757 (Michael Kolupaev).
• Reduce per-query overhead for simple SELECT queries (parsing, analysis and planning). For example, SELECT count() FROM hits from a single connection is roughly 50% faster. #104513 (Raúl Marín).
• Optimize primary key index analysis for long and high-cardinality primary keys. For a long primary key, the run time of index analysis now mainly depends on the complexity of the query's filter (the key columns it actually uses), not on the length of the primary key — so extending the sorting key has negligible extra overhead on index analysis for queries that filter on only a few of its columns. For a high-cardinality primary key, where ClickHouse keeps only a selective prefix of the key columns in memory and does not load the trailing ones, index analysis now works on just that in-memory prefix instead of the whole key. The optimization is enabled by default and can be turned off with the new setting use_lightweight_primary_key_index_analysis. Closes #65103. #91836 (Nihal Z. Miaji).
• The default x86 build now targets x86-64-v3 (AVX2) instead of x86-64-v2 (SSE4.2). This requires a CPU with AVX2 support (Intel Haswell or later, AMD Excavator or later). If your CPU does not support AVX2, use the amd64compat build which targets plain x86-64. #105019 (Raúl Marín).
• Use ipnsort and driftsort (stable sorting) — C++ ports of the Rust standard library's sort implementations — for the general-purpose comparison sorts. Speeds up ORDER BY on non-numeric columns and stable sorts, and removes a worst case on reverse-sorted input. #106650 (Alexey Milovidov).
• New GROUP BY optimization for high cardinality evenly distributed keys that scatters rows across threads by hashing the grouping key, so each thread aggregates a disjoint subset of keys without a merge phase. Set enable_sharding_aggregator = 1 to enable it. #104233 (Nihal Z. Miaji).
• Enable hash table prefetching for string key GROUP BY queries, improving high-cardinality string aggregation performance by ~8%. #101007 (Le Zhang).
• Reduced peak memory usage when merging partial two-level aggregation results with large aggregate states (e.g. groupArray), by freeing each bucket's source states incrementally during the merge instead of keeping them all alive until the merge completes. #102330 (Yuri Fedoseev).
• Memory representation of Enum DataType was optimized. Memory footprint of tables that have Enum type in it can improve up to 10x times for Enum component. Operation time to retrieve name by value(number) is similar or faster. Search by name is slightly slower, but this access direction is less common. #95668 (Ilya Yatsishin).
• Add identifier resolution caching to prevent duplicate identifier resolution during query analysis. #88043 (Max Justus Spransy).
• Improve performance of query analysis for queries over tables with many columns: avoid computing column node hashes (which include the whole source table expression) when not needed. Analyzing nested SELECT * subqueries over a table with ~1200 columns is now about 50 times faster. #106957 (Dmitry Novik).
• Sped up query analysis for queries with many or deeply nested function calls by removing a redundant query-tree hash from the function resolution cache. #107516 (Dmitry Novik).
• Fixed long login and query-startup stalls with replicated access storage when many access entities (row policies, roles, quotas, settings profiles) change at once. Each per-entity cache now recomputes once per notification batch instead of once per changed entity, removing quadratic work that could hold the access lock for minutes. #107672 (Azat Khuzhin).
• Share the hash join's FixedHashMap as the join runtime filter on the probe side. When the build-side hash table is (or can be converted to) a FixedHashMap, it is published as the runtime filter and replaces the Set/BloomFilter that BuildRuntimeFilterStep would otherwise install. Controlled by the new setting join_runtime_filter_from_fixed_hash_table (default true). #105640 (Xiaozhe Yu).
• Lazy application of selector and replication indexes in case of JOIN followed by a selective LIMIT or TopN or another JOIN. To control the number of payload columns for enabling lazy selector indexes use the setting query_plan_min_columns_for_join_lazy_indexing (0 means the optimization is disabled). To control the LIMIT for which the optimization is applied use the setting query_plan_max_limit_for_join_lazy_indexing. #106566 (Hechem Selmi).
• DP (dynamic programming) JOIN reordering is now allowed with parallel replicas. #105889 (Nikita Taranov).
• Improved query plan when JOIN uses runtime filters (default-on enable_join_runtime_filters): the join-reorder cost model now sees through WindowTransform (and other row-preserving plan steps) on the right subtree and uses the underlying row count and per-column NDV instead of falling back to no statistics. #107229 (UnamedRus).
• De-virtualize the emission of non-joined rows in RIGHT and FULL join by batching them. #105679 (Hechem Selmi).
• Support packed keys32 and keys64 methods in HashJoin. #107202 (Nikita Taranov).
• Support packed keys32 and keys64 methods in Set. #107564 (Nikita Taranov).
• More optimal handling of nullable columns in aggregation. #106015 (Nikita Taranov).
• Improve performance of LIMIT BY queries. #103349 (Nihal Z. Miaji).
• Speed up ORDER BY ... LIMIT BY queries by running LIMIT BY inside each parallel sorted stream during Sort when LIMIT BY's columns are a prefix of the ORDER BY. This reduces the number of rows flowing through the final sort merge and any downstream pipeline steps. This optimization is controlled by the new setting query_plan_push_limit_by_into_sort (enabled by default). #104000 (Nihal Z. Miaji).
• Speed up SELECT ... LIMIT N BY <cols> queries when <cols> are a prefix of the table's sorting key, or become one after WHERE col = const fixes leading columns. With this enabled the MergeTree reads data in primary-key order and LIMIT BY first filters in streaming mode with O(1) memory per sorted stream which filters out most of the data, then finally running normal LIMIT BY on reduced data to get the final result. Controlled by the new setting optimize_limit_by_in_order (enabled by default). #105135 (Nihal Z. Miaji).
• Speed up LIMIT BY queries on partitioned MergeTree tables by running LIMIT BY inside each partition's stream in parallel, instead of merging all streams into one before applying the limit. This applies when the partition expression is a deterministic function of the LIMIT BY columns, so no LIMIT BY group can span two partitions. Controlled by the new setting allow_limit_by_partitions_independently (enabled by default). #105126 (Nihal Z. Miaji).
• Speed up LIMIT BY queries by removing redundant key expressions: a key that is a deterministic function of the other keys is dropped (e.g. LIMIT 5 BY x, f(x) becomes LIMIT 5 BY x), and an injective function of a key is replaced by its argument (e.g. LIMIT 5 BY toString(x) becomes LIMIT 5 BY x). This evaluates fewer and cheaper expressions per row. Controlled by the new settings optimize_limit_by_function_keys and optimize_injective_functions_in_limit_by, both enabled by default. #106818 (Nihal Z. Miaji).
• Speed up sharded aggregation, grace_hash join bucketing, and parallel window partitioning by replacing per-chunk column hashing with a kernel that uses hardware CRC32C. #106538 (Harikrishnan Prabakaran).
• Optimize L1Distance, L2Distance, L2SquaredDistance, LinfDistance, and cosineDistance for array arguments with multi-target auto-vectorization on x86-64-v4/v3. For non-const array arguments, all of these except LpDistance, which uses std::pow with a runtime exponent, can now use compiler-vectorized kernels. The existing AVX-512 and Sapphire Rapids BFloat16 const-argument fast paths for L2Distance and cosineDistance are preserved. #101310 (Peng).
• Improved performance of the {Norm}Distance and dotProduct functions. #106007 (Nikita Taranov).
• Improved performance of the arrayNorm function. #106211 (Nikita Taranov).
• The performance of dotProduct improved in some cases. #106210 (Nikita Taranov).
• Improved performance of the AVX-512 const-left paths for L2Distance and cosineDistance on Array(Float32), Array(Float64), and Array(BFloat16) when the array length is exactly divisible by the vectorized processing width. #104625 (Sergey Kuznetsov).
• Enabled AVX-512 codegen for amd and better codegen for arrayDistance. #106505 (Nikita Taranov).
• Improved performance of the L2DistanceTransposed and cosineDistanceTransposed functions for the QBit data type. #106701 (Raufs Dunamalijevs).
• Improve performance of the encrypt, decrypt, tryDecrypt, aes_encrypt_mysql, and aes_decrypt_mysql functions by up to an order of magnitude, recovering the performance lost in the BoringSSL to OpenSSL 3.x migration (24.4). #107339 (Konstantin Bogdanov).
• Improve performance of the encrypt, decrypt, and halfMD5 functions by avoiding implicit per-row OpenSSL provider lookups in OpenSSL 3.x. #99105 (Konstantin Bogdanov).
• Add SIMD implementation of SHA1 that hashes multiple inputs in parallel using AVX-512, improving throughput. #105459 (Joanna Hulboj).
• Added an AArch64 ASIMD/NEON backend for the multi-buffer MD5 implementation. #105563 (Venkata Vineel ).
• Squash source blocks before calculating projection during MATERIALIZE PROJECTION to reduce the number of temporary projection parts and merge overhead. ~3.4x speedup on a 50M-row table. #100047 (Amos Bird).
• Reduced INSERT latency for MergeTree tables with skip indices on ORDER BY columns by avoiding redundant column permutations during part writing (~17% on traces-shaped workloads). #101101 (Amos Bird).
• Enabled Arrow's SIMD code paths (NEON on ARM, SSE4.2/AVX2/AVX512 on x86) and used them to speed up decoding of BYTE_STREAM_SPLIT-encoded Parquet FLOAT/DOUBLE columns. #106376 (Raúl Marín).
• Improved insertion performance for LowCardinality columns with bloom_filter indexes. #106410 (Michael Jarrett).
• Parallelize blob copies in DiskObjectStorageTransaction::copyFile using a per-disk thread pool. #105089 (Asya Shneerson).
• Avoid reading file contents when using the One input format with file-like table functions such as file and s3. #105157 (Yue Ni).
• Speed up clickhouse startup on macOS by about 3x by not exporting dynamic symbols, which the dynamic linker would otherwise process on every launch. #107768 (Raúl Marín).
• Speed up filesystem cache loading on startup by avoiding a redundant directory open per cache key. #107414 (Alexey Milovidov).
• Speed up filesystem cache loading on startup by letting directory-listing threads help load cache metadata once listing is finished, instead of leaving half the threads idle. #107416 (Alexey Milovidov).
• Reduced clickhouse process startup overhead by updating the bundled WasmEdge library, which no longer generates a random hash secret in a global initializer at every startup. #107869 (Raúl Marín).
• The MergeTree primary key and skip indexes can now prune granules for filters where ifNull or coalesce wraps a condition, such as ifNull(key = 0, 0) or coalesce(key = 0, 0). Such predicates — often emitted by query generators to turn a possibly-NULL comparison into a definite boolean — were previously opaque to index analysis and could not skip granules. This extends the existing allow_key_condition_coalesce_rewrite setting (enabled by default). Closes #106264. #106272 (Andy Zhao).
• Skip index evaluation on DateTime64 types should consume lesser CPU in 26.6. #107707 (Shankar Iyer).
• Improved performance of text index analysis in multi-token searches by optimizing handling of rare tokens. #98226 (Anton Popov).
• Use a cache for the posting-list compressed segments of the text index. #106299 (Anton Popov).
• Improved the performance of generic exclusion search for queries that select large consecutive ranges of the table. #93813 (Michael Jarrett).
• S3 clients with the same endpoint and bucket share a cache, avoiding duplicate region discovery. Closes #92482. #96802 (Andrey Zvonov).
• If a query contains a has(<constant array>, <expr>), the analyzer will transform the node to use a faster in implementation if it is feasible to do so. #97341 (Shankar Iyer).
• When a new job is scheduled in ThreadPool, wake the most recently idle worker thread (LIFO) instead of an arbitrary one. This reduces memory fragmentation from per-thread allocator caches. The order in which jobs are processed is not changed. #100177 (Alexey Milovidov).
• Improved performance of approximate runtime filters and bloom filter indexes. #100201 (Christoph Viebig).
• Allow ASOF JOIN to use the parallel_hash join algorithm, parallelizing the build across distinct equality-key values. Previously ASOF was unconditionally opted out of parallel_hash. #105375 (Greg Maher).
• Avoid reading unbounded inputs for INTERSECT and EXCEPT queries when an empty input makes the result known to be empty. #105393 (Yue Ni).
• Add constinit for various MemoryTracker blockers. #105490 (Azat Khuzhin).
• Improve performance of bitmapContains for non-UInt64 groupBitmap states by avoiding repeated rb_max calls during range checks. #105960 (Yue Ni).
• Faster discontinuous queries for LowCardinality columns backed by a single dictionary. #103662 (Ivan Babrou).
• Added a fast path for the HashJoin probe when the block has a single row. #106008 (Nikita Taranov).
• Predicates from queries like SELECT ... FROM view(SELECT ... FROM remote(...)) WHERE ... are now pushed into the query sent to the remote shard. The optimization allow_push_predicate_ast_for_distributed_subqueries lacked a case for table functions. #105986 (Nikolai Kochetov).
• Turn on enable_join_transitive_predicates by default. #103724 (Alexander Gololobov).
• Added support for functions multiSearchAny, multiSearchAnyUTF8, and multiMatchAny in text indexes. Also improved text index analysis for the function match: now patterns with alternative groups can skip more granules. #106279 (Anton Popov).
• Allow filters introduced after the initial PREWHERE selection (predicate pushdown, runtime filters, or explicit PREWHERE plus a WHERE set by the planner) to be merged into the existing PREWHERE on a second optimizer pass instead of staying as a separate Filter step above the MergeTree read. #105445 (Yarik Briukhovetskyi).
• The QueryConditionCache now records individually filtered-out granules even within read batches that partially pass PREWHERE, reducing the number of marks re-read by subsequent queries with the same condition. #105335 (Han Fei).
• Added Keeper setting nuraft_use_bg_thread_for_snapshot_io, enabled by default, to make NuRaft read snapshot objects from a background thread instead of Raft worker threads. #106285 (Antonio Andelic).
• Reduce peak memory usage when applying received snapshots in ClickHouse Keeper with KeeperMemoryStorage. #105851 (Antonio Andelic).
• Route LLVM/JIT allocations to a dedicated jemalloc arena. Reduces RSS fragmentation caused by interleaving long-lived JIT bookkeeping with short-lived query allocations. Adds new asynchronous metrics jemalloc.jit_arena.active_bytes, jemalloc.jit_arena.dirty_bytes, CompiledExpressionCacheBytesMax, and CompiledExpressionCacheCountMax for observability. SYSTEM DROP COMPILED EXPRESSION CACHE now also drops the underlying CHJIT instances and purges the JIT arena. #104113 (Raúl Marín).
• Fix excessive memory reservation when reading sparse dictionary-encoded Nullable(String) columns from Parquet with the native V3 reader. #102805 (Francisco).
• Fixed CREATE TABLE ... CLONE AS (and REPLACE / ATTACH PARTITION ... FROM) on encrypted disks copying data instead of hardlinking it. #106731 (Nikita Mikhaylov).
• Improve cardinality estimation in the query plan optimizer: a column produced by a deterministic single-argument function (e.g. toYear(date)) now inherits its argument's number of distinct values as an upper bound instead of being left without statistics, leading to more accurate join reordering. #107757 (Alexander Gololobov).
• Reduced CPU overhead of asynchronous logging under high log rates by notifying the log consumer only on the empty-to-non-empty queue transition instead of on every message. #107352 (Nikita Mikhaylov).
• Remove duplicate calculations during query execution in more scenarios. #106113 (Yarik Briukhovetskyi).
• Parallelize the processing of a recursive CTE's result: a GROUP BY or other operation over a large WITH RECURSIVE result is no longer limited to a single thread. #107694 (Alexey Milovidov).
• Improved the performance of case-insensitive substring search (positionCaseInsensitiveUTF8, ILIKE, multiSearchAnyCaseInsensitiveUTF8, and related functions) by adding a NEON SIMD path on ARM and a wider AVX2 kernel on x86. #107882 (Raúl Marín).
• Fixed a ~16% throughput regression of the FPC floating-point codec on ARM that was introduced when its predictor tables started using VectorWithMemoryTracking. #108182 (Groene AI).

Improvement

• The background MemoryWorker now periodically updates the server's hard memory limit based on the current memory usage and the amount of memory the kernel reports as available, so ClickHouse leaves room for other processes running on the same host. The formula is (resident memory + system MemAvailable) * max_server_memory_usage_to_ram_ratio. The same max_server_memory_usage_to_ram_ratio server setting controls both the startup cap and the dynamic adjustment; set it to 0 to disable both. To keep only the static startup/reload cap (the behavior of previous versions), set the new server setting memory_worker_dynamic_hard_limit to 0. #104964 (Alexey Milovidov).
• Support C# PostgreSQL client in PostgreSQL protocol. This closes #18611. #80785 (Konstantin Vedernikov).
• Mutations now use the analyzer. #98884 (Nikolai Kochetov).
• Added granular control over query echoing in the CLI. The --echo option now accepts an optional boolean value and works in both interactive and batch mode. New options --echo-formatted and --echo-query-id control whether echoed queries are formatted and whether the query_id is printed, respectively. The --hilite/--highlight option now also controls highlighting of echoed queries. As a side effect, --echo is now a boolean-value option, so a positional query directly after a bare --echo is treated as its value; use --echo --query "..." or --echo=false instead. #106191 (Alexey Milovidov).
• Support schema evolution together with concurrent consistency checks for data lake catalogs. #106102 (Konstantin Vedernikov).
• Allow cache disk for datalake table engines. #102017 (RinChanNOW).
• Fix DataLakeCatalog databases with catalog_type = 'onelake' reading table data by using the OneLake Blob endpoint (.blob.fabric.microsoft.com) by default. Set onelake_use_blob_endpoint = false to keep the previous DFS endpoint (.dfs.fabric.microsoft.com) behavior. #106843 (Konstantin Vedernikov).
• Update default of S3(Azure)Queue setting persistent_processing_node_ttl_seconds from 1 hour to 6 hours (which stands for cleanup time due to service unclean restart etc). The previous default was fine for processing nodes ttl, but it is also used for bucket lock ttl, which can be hold for longer time, therefore 1 hour was not enough. #106838 (Kseniia Sumarokova).
• Decreased the default size of the Iceberg metadata cache from 1 GB to 128 MB. #106492 (Konstantin Vedernikov).
• Propagate the S3Queue streaming task query_id to dependent table inserts. #106494 (Christoph Wurm).
• Populate used_storages in system.query_log with the storage engine name when querying tables via DataLakeCatalog. #100706 (Melvyn Peignon).
• You can check which 'operation' and what 'summary' Iceberg's snapshots have. Useful for testing and debugging. #106246 (Den Kalantaevskii).
• Complete the final S3 multipart upload request asynchronously via the task tracker, so it can overlap with the last part upload instead of running serially in finalize. #105487 (Asya Shneerson).
• Added four new MergeTree table settings to control default parameters of text indexes: text_index_dictionary_block_size, text_index_dictionary_block_frontcoding_compression, text_index_posting_list_block_size, and text_index_posting_list_codec. These settings allow tuning text index behavior at the table level without specifying parameters in every index definition. Explicit per-index arguments still take precedence. #100626 (Anton Popov).
• Allow projections to override additional MergeTree settings (compression, part format, serialization) beyond just index_granularity, with an allow-list of allowed settings and validation. #101170 (Amos Bird).
• Add current_projection, current_projection_progress, projections_completed, and projections_remaining columns to system.merges to expose projection merge progress. #102611 (Amos Bird).
• Fixed PREWHERE with IN subquery on primary key columns not using primary key index for granule pruning, causing full table scans instead of reading only relevant granules. #102570 (Nikita Mikhaylov).
• Function h3PolygonToCells now enforces the maximum array size across all polygons of a MultiPolygon, validates the underlying H3 library return codes, and rejects MultiLineString arguments instead of silently returning an empty result. #106399 (Raúl Marín).
• Add a new keeper-only system.keeper_snapshots table with information about local ClickHouse Keeper snapshots. #105571 (Miсhael Stetsyuk).
• Add a new keeper-only system.keeper_changelogs table with information about local ClickHouse Keeper changelog (Raft log) files. #105617 (Miсhael Stetsyuk).
• Add a keeper-only system.keeper_cluster table. Contains one row per Raft cluster member as seen by the current Keeper. #105646 (Miсhael Stetsyuk).
• Add more Keeper profile (server-side + client-side) events for watches. Closes #97703. #105336 (Konstantin Vedernikov).
• Added Keeper coordination_settings for NuRaft uncommitted log entry admission limiting and append-entries backward-probe throttling. #106108 (Antonio Andelic).
• Add enable_compression setting for the mysql table function, the MySQL table engine, the MySQL database engine, dictionary SOURCE(MYSQL), and named collections. When enabled, ClickHouse negotiates MySQL protocol-level compression for all data transferred over the connection. #103229 (Bernard Lim).
• Reduced cancellation latency for queries running over the PostgreSQL wire protocol: KILL QUERY now interrupts output serialization within a single chunk instead of waiting for the entire chunk to be sent to the client. #106535 (Roman Vasin).
• Reduced cancellation latency for queries running over the MySQL wire protocol: KILL QUERY now interrupts output serialization within a single chunk instead of waiting for the entire chunk to be sent to the client. #107228 (Roman Vasin).
• Fixed reading of the auth_response length in the MySQL handshake, where a length byte >= 128 was interpreted as a multi-gigabyte value because it was read as a signed char. #107384 (uwezkhan).
• MaterializedPostgreSQL now maps PostgreSQL numeric(p, 0) columns with precision greater than 76 (e.g. numeric(78, 0) used for 256-bit integers) to ClickHouse Int256 instead of failing with "Precision too big". Values that do not fit into Int256 are rejected with a clear error. #107431 (Alexey Milovidov).
• Send an exception to the client when TCP connection setup fails. #107317 (Nikolai Kochetov).
• Users can now insert Avro Fixed fields for 8-bit/16-bit/32-bit/64-bit integer variants. #98139 (Patrick Pichler).
• The AvroConfluent format now retries the Confluent Schema Registry HTTP client on transient failures (transport timeouts, connection refused, DNS errors, HTTP 5xx/408/429) with exponential backoff, instead of aborting the INSERT on the first network glitch. New settings format_avro_schema_registry_max_retries (default 5) and format_avro_schema_registry_retry_initial_backoff_ms (default 100) control the policy. Schema-validation errors (HTTP 409, malformed Avro JSON) remain fatal. #106661 (Groene AI).
• Record privileges in system.query_log.used_privileges for all granted access checks, including those that go through the non-throwing isGranted path (checkAccessWithFilter). Previously only privileges checked via throwing entry points (checkAccess / checkGrantOption) were recorded, which made READ ON FILE / READ ON S3 / READ ON AZURE / READ ON URL invisible in the audit log for DESCRIBE, CREATE TABLE AS, and similar queries that use file / s3 / azure / url table functions. Access enforcement is unchanged. #104693 (Alexey Bakharew).
• Added asynchronous metrics TotalUncompressedBytesOfMergeTreeTables and TotalUncompressedBytesOfMergeTreeTablesSystem, reporting the total uncompressed size of data stored in MergeTree-family tables. #106364 (Alexey Milovidov).
• Adds the GlobalMemoryLimitExceeded profile event so operators can monitor when the server-wide memory limit is hit. #106466 (Sacheendra Talluri).
• Populate the ExecutableUserDefinedFunction* ProfileEvents counters for executable_pool UDFs. Per-call invocation count, wall and pool-wait time, child-process CPU and peak memory, and stdin/stdout bytes are now visible in system.query_log.ProfileEvents. #105010 (Xu Jia) #105618 (Ilya Andreev).
• Added asynchronous metrics ExecutableUserDefinedFunctionMemoryResidentBytes and ExecutableUserDefinedFunctionProcesses, reporting the resident memory (VmRSS) and number of live processes of executable and executable_pool user-defined functions, including descendant processes and idle pool workers. #107300 (Hanzi Jiang).
• Added three Linux-only async metrics — MemoryThreadStacksCount, MemoryThreadStacksVirtual, and MemoryThreadStacksResident — that report pthread stack memory separately from the rest of anonymous memory. Enabled via asynchronous_metrics_enable_heavy_metrics. Requires Linux 5.17+ (prctl(PR_SET_VMA_ANON_NAME)) and readable /proc/self/smaps; otherwise the metrics are absent and the limitation is reported in system.warnings. #106230 (Raúl Marín).
• Expose the MemoryThreadStacks* asynchronous metrics (resident/virtual size and count of thread stacks) on macOS. #107752 (Raúl Marín).
• Table engines now carry embedded documentation, introspectable via the new description, syntax, examples, introduced_in, and related columns of the system.table_engines table. #106177 (Alexey Milovidov).
• Database engines now carry embedded documentation, introspectable via the new description, syntax, examples, introduced_in, and related columns of the system.database_engines table. #106178 (Alexey Milovidov).
• Data types now carry embedded documentation, introspectable via the new description, syntax, examples, introduced_in, and related columns of the system.data_type_families table. #106180 (Alexey Milovidov).
• Input/output formats now carry embedded documentation, introspectable via the new description, examples, introduced_in, and related columns of the system.formats table. #106181 (Alexey Milovidov).
• Aggregate function combinators now carry embedded documentation, introspectable via the new description, syntax, examples, introduced_in, and related columns of the system.aggregate_function_combinators table. #106185 (Alexey Milovidov).
• Added the --chime command-line option to clickhouse-client, clickhouse-local, and the embedded client. When a query finishes (on success or on error) after running for at least N seconds, the client writes the ASCII BEL control character (\x07) to stderr. Terminals decide whether to make a sound or a visual flash based on the user's preferences. Enabled by default with a 5-second threshold; pass --chime N for a custom threshold or --chime 0 to disable. Closes #92718. #104545 (Groene AI).
• In clickhouse-client, when the terminal does not support bracketed paste, embedded newlines from a pasted multi-line query are now folded into the same edit buffer instead of switching to the continuation prompt for every line. The pasted query stays under a single prompt and the arrow keys navigate across its lines. This is a best-effort improvement that relies on the typical TTY-buffered paste behavior. #104299 (Alexey Milovidov). Now also works with syntax highlighting disabled (--highlight 0). #106665 (Alexey Milovidov).
• Add MySQL-style runtime pager control for clickhouse-client/clickhouse-local. #105706 (Azat Khuzhin).
• clickhouse-client now respects non-UTF-8 terminals: when the terminal character encoding is not UTF-8 (e.g. with LANG=C), the Pretty formats fall back to ASCII grid borders instead of printing Unicode box-drawing characters that would corrupt the terminal. #106213 (Alexey Milovidov).
• Sanitize server-supplied display strings in clickhouse-client's Hello packet handling (server name, time zone, display name, password-rule patterns and messages) so a hostile server cannot inject bytes that the client renders verbatim, and cap their size to defend against unbounded allocation. #105243 (Raúl Marín).
• The Web UI now displays the result as an image when a query uses an image output format such as FORMAT PNG, instead of showing the raw bytes as a table. #107638 (Alexey Milovidov).
• Add setting output_format_pretty_use_nbsp_for_padding to render table-layout padding in table-style Pretty formats as U+00A0 NO-BREAK SPACE when output_format_pretty_grid_charset is UTF-8. This helps copied Pretty output keep table alignment in tools that collapse regular spaces. The setting is disabled by default, and ASCII charset output keeps regular spaces. #103559 (Ashrith Bandla).
• The universal install script now also installs clickhousectl into ~/.local/bin on Linux and macOS, with a chctl symlink. Set CLICKHOUSE_ONLY=1 to skip. #105399 (Alasdair Brown).
• Fixed a spurious Syntax error: Unterminated quoted string that could occur intermittently when installing ClickHouse via curl https://clickhouse.com/ | sh while a clickhouse binary already existed in the current directory. #106417 (Alexey Milovidov).
• Fix the left panel height on the play.html page when the web terminal is open, so the terminal toggle button at the bottom stays visible. #105087 (Alexey Milovidov).
• Avoid selecting the only query in the Web UI after running it. #105711 (Joey Yu).
• The Web SQL UI now expands the query editor when a query is at most 30% taller than the current editor height. #105713 (Joey Yu).
• In the Web UI, lay out the bottom menu icons (Web Terminal and GitHub) horizontally when the left panel is expanded, giving the list of databases and tables more vertical space. #106427 (Alexey Milovidov).
• In the Web UI (play.html), pressing Escape now deactivates the currently selected result-table cell. #107777 (Alexey Milovidov).
• Improvements to the database panel in the Web SQL UI (Play): a tooltip on the database icon, a button to hide the panel, full-width clickable database/table names, and a fix for the panel width shifting when the scrollbar appears. #108013 (Alexey Milovidov).
• Add a server setting (min_allocation_size_to_throw_on_memory_limit) to allow any allocation to throw MEMORY_LIMIT_EXCEEDED, this should help with preventing OOMs. #105265 (Azat Khuzhin).
• Allow NONE authentication for SSH (prevents asking password for no_password users). #105476 (Azat Khuzhin).
• Reset the supplementary group list in clickhouse su before dropping privileges, matching the behavior of /bin/su and sudo. Previously the dropped process inherited the invoker's supplementary groups. #105247 (Raúl Marín).
• Add BFloat16 support for numeric predicate (isFinite, isNaN) functions. #105391 (Mohamed Hussain S).
• Reduce memory usage of polygon dictionaries (polygon_index_cell, polygon_index_each) and make system.dictionaries.bytes_allocated correctly reflect the lookup index they build. #105431 (Raúl Marín).
• Fixes Kafka table engine consumers that kept using a short poll interval after partition assignment, so they return to the configured kafka_poll_timeout_ms and avoid excessive empty polls, smaller inserted parts, and extra merge overhead after rebalances. #100431 (sugaf1204).
• Identify columns by position (instead of by name) when removing unused columns in the query plan. This enables unused-column removal when duplicated column names are present. #100586 (János Benjamin Antal).
• ClickHouse throws a proper exception for attempts to use table_readonly for replicated engines, with better exception handling for DDL queries (and DatabaseReplicated) related to this setting. #100950 (alesapin). OPTIMIZE TABLE ... ON CLUSTER and other DDL no longer hang when the target table has table_readonly = 1. The setting now throws a new dedicated error code TABLE_IS_PERMANENTLY_READ_ONLY, which DDLWorker treats as non-retriable (distinct from the transient TABLE_IS_READ_ONLY that arises during temporary ReplicatedMergeTree ZooKeeper disconnects). The table_readonly setting is also now explicitly rejected for ReplicatedMergeTree, both at creation and via ALTER MODIFY SETTING. Follow-up to #97652. #105109 (Alexey Milovidov).
• Fixed refreshable materialized view refreshes that could fail with UNKNOWN_TABLE after the target table had been replaced (for example via EXCHANGE TABLES or drop-and-recreate): the refresh now resolves the target table by name instead of relying on a stale UUID. #102724 (Seva Potapov).
• Added a setting wait_for_part_commit_in_dependent_materialized_views (default false). When a materialized view's SELECT reads back from its own source table (for example via an INNER JOIN to the source), the cascade could miss the row currently being inserted, because the inserted part is committed only after the dependent views run. Enabling this setting commits the part before the dependent views are triggered, so they observe the in-flight row, at the cost of less insert parallelism. #105943 (Elmi Ahmadov).
• Do not swallow fatal errors (e.g. MEMORY_LIMIT_EXCEEDED) in tryDeserialize. #106808 (Azat Khuzhin).
• Check CREATE TEMPORARY TABLE grant lazily in InverseDictionaryLookupPass. #107098 (Azat Khuzhin).
• Fix an ILLEGAL_TYPE_OF_ARGUMENT error for distributed queries with serialize_query_plan = 1 that contain a lambda with a constant argument (e.g. arrayMap(t -> t.2, ...)). Constant columns of ActionsDAG INPUT nodes are now preserved during query plan serialization. #107124 (Alexey Milovidov).
• Deserialization of the states of the contingency, cramersV, cramersVBiasCorrected, and theilsU aggregate functions now validates that the stored counts form a consistent contingency table and throws a CORRUPTED_DATA exception otherwise. Closes #106899. #107185 (Nihal Z. Miaji).
• Preserve original error codes for exceptions wrapped in arrow::Status. #107267 (Azat Khuzhin).
• Support keyed_by_normalized_query_hash for quotas defined in the static server configuration (users.xml), matching the existing CREATE QUOTA ... KEYED BY normalized_query_hash DDL syntax. #107654 (Alexey Milovidov).
• The compatibility setting no longer applies obsolete settings, so it does not mark them as changed or produce obsolete-setting warnings. #107737 (Maxim Orlovsky).
• Async inserts no longer log the full list of query_ids at trace/debug level, which since 26.2 could blow up text_log on services with heavy async insert traffic. Detailed lines are now at test level. #107852 (Sema Checherinda).
• Filesystem cache improvement: stop invalidated priority entries from pinning KeyMetadata. Follow up to #106387. #107903 (Kseniia Sumarokova).
• FileCache metrics improvement. #106116 (Kseniia Sumarokova).
• Do not print the "Stack trace (when copying this message, always include the lines below):" preamble in exception messages when the stack trace is actually empty. #106524 (Alexey Milovidov).
• Fix a potential overflow in roundUpToMultiple when computing filesystem cache boundary alignment for very large offsets. #92579 (Bharat Nallan).
• EXPLAIN SYNTAX now formats operators as function calls consistently in explain output (for example plus(1, 2) instead of 1 + 2). #94681 (Mohamed Abdelhalim ).
• Improved table name hints in error messages: no longer suggests the exact same name, and includes the database name in the suggestion (e.g., "Maybe you meant other_db.my_table?"). #95116 (Mathuranath Metivier).
• Improved error message for unresolved identifiers in queries without a FROM clause to suggest adding one. #101769 (Yash ).
• Add EXPLAIN PIPELINE option to compact repeated processor chains. #104662 (Yue Ni).
• Fix a heap-buffer-overflow read in syntax-error message construction (UTF8::computeWidthImpl via parseQuery.cpp) that occurred when the parser had backtracked past the first semicolon / end-of-stream token; release builds were splicing bytes from neighboring heap memory into the displayed error, ASan builds aborted. #105086 (Groene AI).
• Make hive partition strategy a default under compatibility setting file_like_engine_default_partition_strategy. #86746 (Kseniia Sumarokova).
• Use a larger (8 MiB) thread stack on macOS to match the Linux default, fixing rare server crashes from stack overflow during JIT compilation. #107033 (Raúl Marín).
• The temporary storage size limit of clickhouse-local is no longer hard-coded to 1 GiB. The default is raised to 1 TiB and can be configured with the max_temporary_data_on_disk_size server setting. #106689 (Alexey Milovidov).
• Add read-checksums command to clickhouse-disks. It reads the checksums.txt file of a MergeTreeDataPart and prints it as a human-readable, tab-separated table. #106901 (Asya Shneerson).
• Added a read-bitmap command to clickhouse-disks. #107834 (murphy-4o).
• Chdig: enable TLS for secure connections (previous leads to either "unknown setting skip_verify" or "connection reset by peer"). #105864 (Azat Khuzhin).
• chdig v26.5.1. #105918 (Azat Khuzhin).
• chdig v26.6.1 - {asynchronous_,}metric_log, query patterns, heatmaps, logs/traces stored on disk (previously it can use >40GiB for 1 hour of traces). #107678 (Azat Khuzhin).
• The server config (programs/server/config.xml) now sets keep_alive_timeout to 30 (formerly 10), aligning with the actual documented and implemented default. #107779 (Dan Checkoway).
• The default for the server setting disk_connections_rcvbuf changed from 0 (kernel TCP autotuning) to 204800 (200 KB), capping the per-socket TCP receive buffer for object-storage (S3/Azure/GCS) disk connections. #107859 (Sema Checherinda).
• The PREWHERE optimizer now groups conjuncts that reference the same column set before estimating selectivity, so that conditions like a > 2500 AND a < 2502 are evaluated together as a combined range rather than as two independent predicates, producing a more accurate selectivity estimate. #106337 (Han Fei).
• Add silk fiber aware secure and plain socket implementations. #107680 (Miсhael Stetsyuk).
• Fixed a garbled error message (swapped arguments) and a typo in the nested function. #108031 (Alexey Milovidov).
• Added a sed command to clickhouse-disks that applies a sed expression to a given path, in-place. #107131 (Asya Shneerson).
• Added the create-time materialized_postgresql_use_extended_date_and_time_types setting for the MaterializedPostgreSQL database engine. By default (enabled), PostgreSQL date/timestamp columns are inferred as Date32/DateTime64; setting it to 0 at CREATE DATABASE time infers the narrower Date/DateTime types. #107428 (Alexey Milovidov).

Bug Fix (user-visible misbehavior in an official stable release)

• Make possible to drop detached parts with the tryN suffix. #58957 (János Benjamin Antal).
• Fix a MULTIPLE_EXPRESSIONS_FOR_ALIAS exception for queries with duplicate projection aliases (for example SELECT *, day + 365 AS day) inside nested subqueries when running with parallel replicas. #80310 (Alexey Milovidov).
• Fix a bug with splitMultipartQuery throwing an "Empty query" error for queries that end with comment after semicolon. #85491 (Yarik Briukhovetskyi).
• Fix an exception with ARRAY JOINs: Function writeSlice expects same column types for GenericArraySlice and GenericArraySink which happens when LowCardinality numeric types are used (issue #57243). #91784 (Jimmy Aguilar Mena).
• Fix NOT_FOUND_COLUMN_IN_BLOCK exception when using LIMIT BY with constant columns alongside DISTINCT and ORDER BY with the new analyzer. #93195 (Ashrith Bandla).
• Fix NOT NULL columns being silently created as Nullable when data_type_default_nullable = 1 and the table is created in a Replicated database or via ON CLUSTER. #97572 (xiaohuanlin).
• Fixed HiveCatalog connection stability by adding automatic retry mechanism and reconnection logic for handling TTransportException errors when communicating with Hive Metastore. #98471 (Dmitriy Borisenko).
• Fixed nested function (used internally by ARRAY JOIN) stripping LowCardinality from column types, causing Array(LowCardinality(String)) to become Array(String) in output. Closes #95582. #98974 (Yash ).
• Fix "Distributed task iterator is not initialized" exception when using url, s3, or similar table functions in queries with parallel replicas enabled. #100146 (Alexey Milovidov).
• Fix logical error exception when reading Iceberg tables whose format version was upgraded by an external tool (e.g. Spark). #100407 (Alexey Milovidov).
• Functions like, ilike, notLike, notILike, and match now support constant haystack with non-constant needle (e.g. 'foo' LIKE pattern_column), which previously threw ILLEGAL_COLUMN. #100479 (Yash ).
• Fixed wrong row count returned by a MaterializedView query with query_plan_enable_optimizations = 0 when the view maps an integer column to a Bool column. #100692 (Maksim Moisiuk).
• Fix an exception (LOGICAL_ERROR: 'PREWHERE passed to format that doesn't support it') when reading Iceberg tables containing ORC data files with PREWHERE optimization enabled. #101206 (Groene AI).
• Fix race in RestCatalog. #101216 (Smita Kulkarni).
• Fix NOT_FOUND_COLUMN_IN_BLOCK error when selecting from a VIEW over a table with a normal projection. #101218 (Amos Bird).
• Fix stale metadata in FileLog when a file is deleted and recreated. #101408 (Azat Khuzhin).
• Fix join reordering silently dropping unmatched rows of a RIGHT/LEFT JOIN when it is comma-joined (cross) with another table, e.g. t1 RIGHT JOIN t2 ON t1.c = t2.c, t3. The query previously returned the inner-join result instead of the outer-join one. #101684 (Groene AI).
• Fixed FORMAT clause being consumed by INSERT instead of applying to EXPLAIN output in EXPLAIN INSERT INTO ... SELECT ... FORMAT .... #101772 (Yash ).
• Fixed incorrect compression codec selection for MergeTree parts when the table-level default_compression_codec setting was explicitly configured. Parts written on insert, during merges, and for projections used the server-wide default codec instead of the table-level setting (the empty part produced by a fully-deleting mutation is now covered as well). #101784 (Yash ).
• Reject negative Float64 values (e.g. -100.5) in workload settings like max_bytes_per_second, max_cpus, etc. Previously only negative integers were validated, allowing negative floats to silently create broken scheduler nodes. Closes #101825. #101842 (Groene AI).
• Fix a LOGICAL_ERROR ("Port is not connected", code 49) that could occur when executing queries involving a VIEW with aggregation inside a JOIN. #102574 (Jimmy Aguilar Mena).
• Fix inconsistent part metadata after mutations of columns with non-default serializations. #102817 (Eduard Karacharov).
• Fix updating metadata before executing mutation resolves #96806. #102882 (Smita Kulkarni).
• Fix SELECT queries being significantly slower when concurrent INSERTs are running. Previously an INSERT pipeline reserved CPU slots up to max_threads at query start even when most slots were never used, starving concurrent SELECTs. CPU slot allocation is now demand-driven: the pipeline only requests slots as it actually pushes parallelizable work. Applies both to concurrency control and to the preemptive CPU scheduler for workloads. New server setting concurrent_threads_lazy_allocation (default true) acts as a rollback lever. #102928 (Seva Potapov).
• Fix NULL propagation when reading subcolumns extracted from Nullable(Tuple(...)) columns. For example, for tup Nullable(Tuple(s Nullable(String))), SELECT tup.s now correctly returns NULL in rows where the outer tuple is NULL instead of garbage values. This covers all element types that can represent NULL: Nullable, Dynamic, Variant and LowCardinality(Nullable(...)). Closes #105356. #102942 (Nihal Z. Miaji).
• Throw INCORRECT_DATA instead of LOGICAL_ERROR when client-supplied data in the Native format is truncated or malformed. #102975 (János Benjamin Antal).
• Added cancellation check to ObjectStorage read operation. Closes #98165. #103016 (Smita Kulkarni).
• Respect input_format_binary_max_type_complexity in decoding aggregate function parameters. Closes #102903. #103026 (Pavel Kruglov).
• Fix nullable inference for geo columns in Arrow-based Parquet reader. Closes #101845. #103032 (Pavel Kruglov).
• Fixed recursiveRemoveLowCardinality erasing custom geometry type names (e.g. LineString vs Ring, MultiLineString vs Polygon), which caused misinterpretation of the geometry type. Closes #103207. #103041 (Joanna Hulboj).
• Fixed input_format_max_block_size_bytes being silently ignored during INSERT parsing when max_insert_block_size_bytes is 0 (the default). The setting now correctly limits the size of blocks produced by row input formats. #103068 (Kirill Kopnev).
• Fixed ClickHouse occasionally producing invalid GSSAPI tokens due to incorrect stripping of trailing null bytes. #103114 (Michael Jarrett).
• Fix analyzer-time constant folding for short-circuit functions (if, multiIf, and, or, etc.) so that statically unreachable branches no longer raise exceptions at analysis time. For example, WITH 0 AS n SELECT multiIf(n = 0, 0, intDiv(100, n)) now correctly returns 0 instead of failing with a division-by-zero error. #103157 (Peng).
• EXPLAIN SYNTAX expands parameterized views. #103263 (Jordi Villar).
• Fix data corruption when writing Parquet (and other trailer-bearing formats such as ORC and Arrow) to HDFS via INSERT INTO FUNCTION hdfs(...). Since 26.1, WriteBufferFromHDFS did not flush its working buffer on finalize(), so the last up to DBMS_DEFAULT_BUFFER_SIZE bytes of every file were silently lost, including the Parquet PAR1 footer. Reading such files returned Not a Parquet file (wrong magic bytes at the end of file). #103268 (Groene AI).
• Fix wrong results and a possible logical error for correlated subqueries when a join size limit (max_rows_in_join / max_bytes_in_join) is set together with join_overflow_mode = 'break'. The join created internally to evaluate a correlated subquery now ignores those user limits, so it can no longer stop early and drop rows. #103322 (Groene AI).
• Fix a bug where ALTER TABLE ... MODIFY SETTING on an EmbeddedRocksDB table could persist an invalid setting value to the table metadata file even when the server rejected the query. On the next server restart the table would fail to attach with CANNOT_PARSE_BOOL (or a similar parsing error), and in databases where load failures are fatal the server would refuse to start. Invalid setting values are now rejected before any metadata is written. #103417 (Groene AI).
• Fixed a server abort when creating a table with an object-storage engine (AzureBlobStorage, DeltaLakeAzure, S3, HDFS) using an unsupported number of arguments. The server now returns a clean NUMBER_OF_ARGUMENTS_DOESNT_MATCH error instead of aborting in debug/sanitizer builds. #103544 (Groene AI).
• Fix a server crash in JSON and Dynamic data type parameter parsing when the abstract syntax tree (AST) was structurally malformed (for example produced by the AST fuzzer): the equals(name, value) parameter expression could be left with fewer than two children, which DataTypeObject and DataTypeDynamic then dereferenced without bounds checking. #103545 (Groene AI).
• Fix logical errors in analyzer with column names collision in lambda used in prewhere. Closes #103584. #103627 (Pavel Kruglov).
• Fix sporadic Logical error: 'Database <name> not found' from DataLakeConfiguration::getCatalog when an Iceberg engine table is loaded inside a regular database during async metadata loading. #103775 (Groene AI).
• Fix MULTIPLE_EXPRESSIONS_FOR_ALIAS errors thrown by remote replicas when running queries that reference projection aliases inside PREWHERE / WHERE / HAVING / QUALIFY (e.g. SELECT x AS a, y AS b, (a AND b) AS c FROM t PREWHERE c) or SELECT * over self-joins with overlapping column names, with parallel replicas and parallel_replicas_local_plan = 0. Closes #74324. #103806 (Groene AI).
• Fix server abort when a query uses nested coalesce/ifNull comparisons (e.g. WHERE coalesce(a, b, coalesce(c, d), e) = const) on a MergeTree table with multiple minmax skip indexes and use_skip_indexes_for_disjunctions = 1. The skip-index rewrite of <op>(coalesce(...), const) is now applied recursively to inner coalesce arguments, so the per-index KeyCondition RPN matches the template's RPN as the disjunction-tracking code already assumes. #103929 (Groene AI).
• Fix max_rows_to_transfer and max_bytes_to_transfer being silently ignored for GLOBAL IN and GLOBAL JOIN queries under the new analyzer. The settings now raise SET_SIZE_LIMIT_EXCEEDED (or break, depending on transfer_overflow_mode) when the materialised external table exceeds the configured limit, matching the behavior of the old analyzer. Closes #103333. #104119 (Groene AI).
• Fix excessive catalog/S3 metadata reads when an INSERT or DDL statement references a non-existent table in a DataLake catalog database with show_data_lake_catalogs_in_system_tables enabled. The typo-hint suggestion path loaded full per-table Iceberg metadata for the whole catalog, which could exhaust memory on large catalogs. #104124 (DQ).
• Fix a crash (LOGICAL_ERROR "Columns are assumed to be of identical types, but they are different in Nullable" in debug builds, a ColumnString::compareAt null-pointer SIGSEGV in release builds) and a wrong result that could occur in queries using direct join_algorithm with a MergeTree right-side table when the lookup plan reordered columns during optimization. The right-side columns could land in wrong-named slots, so a filter or comparison on the join key saw a column of the wrong type. Surfaced by AST fuzzer as STID 2139-5111 and reported in #107272. #104174 (Groene AI).
• Reject out-of-range integer partition ID for Date instead of silent overflow or LOGICAL_ERROR on ALTER. #104250 (Azat Khuzhin).
• Disable additional_table_filters with parallel replicas and the analyzer without query plan serialization. Previously it could lead to incorrect results. #104296 (Azat Khuzhin).
• Fix dictGetOrNull silently overwriting other columns in the SELECT projection with NULL when called with a Nullable key column whose values are missing in the dictionary. The function was mutating an input-aliased null map in place; it now deep-clones the result column before mutation. Closes #73633. #104327 (Groene AI).
• Fix a broken patch part after ALTER TABLE ... DROP PARTITION ID 'patch-...' followed by DETACH/ATTACH TABLE. Previously the empty covering part was written without partition.dat and source_parts.dat, leading to a broken-on-start_patch-... entry in system.detached_parts after the next attach or server restart. Closes #93132. Closes #102103. #104353 (Groene AI).
• Fixed streaming INSERT with input_format_max_block_wait_ms for the HTTP interface and for INSERT SELECT FROM input, so partial input blocks are flushed before the request finishes. #104534 (Alexey Milovidov).
• Fixed a bug where queries combining arrayJoin with ORDER BY ... LIMIT after a JOIN could silently return zero rows. The query plan optimization that lifts function evaluation above the SortingStep no longer applies when the lifted expression contains arrayJoin, since arrayJoin can change the number of rows. Closes #82279. #104558 (Groene AI).
• Fix a rare server abort during MergeTree family table destruction. The abort could occur when shutdown raised an exception before the background-job scheduler was fully stopped: a background task firing in that narrow window would dispatch a virtual call through a partially-destroyed storage object and hit __cxa_pure_virtual. #104561 (Groene AI).
• Fix inconsistent result in JSON combined subcolumn with a type hint containing null value. #104584 (Pavel Kruglov).
• Fix wrong results or missed projection when an aggregate projection contains multiple sumIf aggregates with different IN (...) conditions. #104765 (Jimmy Aguilar Mena).
• Fix wrong row count from arrayJoin() used inside JOIN ON: the result was multiplied by the array length an extra time. #104785 (Shaohua Wang).
• Fix deltaSumTimestamp returning wrong results for signed integer types crossing zero. Resolves #104750. #104830 (Konstantin Bogdanov).
• Fix block structure mismatch in UnionStep after filter push-down with NULL constants. Closes #104821. #104853 (Pavel Kruglov).
• Fix Logical error: 'Metadata is not initialized' raised by DELETE FROM on a freshly-attached Iceberg, DeltaLake, or Hudi table whose metadata file is corrupted or unloadable. A regular user-facing exception is reported instead, and the server keeps running. Closes #104891. #104917 (Groene AI).
• Fixed the max_memory_usage_soft_limit was not updated on-the-fly when the configuration changed. The soft memory limit was calculated once at startup and cached, so subsequent config reloads had no effect. After this fix, the limit is recalculated and applied immediately on every config reload, no Keeper restart required. #104940 (Kai Zhu).
• Fix JIT symbol resolution on macOS so that sort, expression, and aggregate JIT compilation no longer fail with CANNOT_COMPILE_CODE: Could not find symbol _<name>. #104946 (Alexei Fedotov).
• Fix an exception (Received signal 6 (abort) in vector hardening, observable as Tuple::back() on an empty vector) when executing a query of the form SELECT ... FROM <Distributed table> WHERE/HAVING/GROUP BY ... (sharding_key_column IN tuple()) with optimize_skip_unused_shards_rewrite_in enabled under the new analyzer. #104966 (Alexey Milovidov).
• Fix a Logical error: 'Inconsistent AST formatting' server abort (STID 1941-1bfa) on queries like CREATE TABLE t (c0 Int CODEC(not((not(materialize(1), materialize(2)))), ZSTD)) ENGINE = Memory in debug / sanitiser builds. The formatter no longer emits redundant outer parens around a multi-argument tuple(...) function call that appears inside CODEC / STATISTICS / BACKUP_NAME argument lists (where the operator form (a, b) is disabled), keeping the format-parse-format round-trip stable. #104991 (Groene AI).
• Fix NOT_FOUND_COLUMN_IN_BLOCK thrown by ALTER TABLE ... MATERIALIZE INDEX on parts that were created in 25.8 and contain a skip index over a column that was added with a separate ALTER TABLE ... ADD COLUMN. The mutation now correctly reads every column required by every pre-existing skip index and projection on the part during force-recalculation. Closes #104872. #105039 (Groene AI).
• Fixed two LOGICAL_ERROR: Reading from materialized CTE 'X' before it has been materialized shapes thrown by queries with enable_materialized_cte: (1) a reused materialized CTE filtered by IN (subquery) over another materialized CTE, and (2) a materialized CTE referenced both directly and inside a WHERE ... IN (...) filter that hits a MergeTree primary key through a nested IN-subquery. EXPLAIN on the same queries was affected too because the bugs fired during plan optimization. Closes #101940, closes #102320. #105041 (Dmitry Novik).
• Fix countmin statistics PREWHERE selectivity estimation for Float32 columns. Two bugs caused countmin statistics to silently produce wrong estimates for Float32 columns: ConditionSelectivityEstimator skipped statistics entirely when the column type (Float32) was narrower than the literal type (Float64), falling back to default selectivity and ignoring the sketch; and StatisticsCountMinSketch::estimateEqual hashed the first N bytes of a Field object, but Field stores Float32 as Float64 (NearestFieldType<Float32> = Float64), so the byte pattern used at query time differed from the actual Float32 bytes stored during build. #105047 (Han Fei).
• ATTACH TABLE name <clauses>; queries that supply storage clauses (ORDER BY, PARTITION BY, PRIMARY KEY, SAMPLE BY, TTL, UNIQUE KEY, or engine SETTINGS) without an ENGINE now throw BAD_ARGUMENTS instead of silently re-attaching the table with its stored definition and discarding the user-supplied clauses. Query-level session SETTINGS (such as log_comment) are still applied. Use ATTACH TABLE t; to re-attach with stored metadata, or ALTER TABLE t MODIFY SETTING ... after ATTACH to change settings. #105068 (Groene AI).
• Fixes a use-after-free in runningAccumulate when called on a column whose aggregate function returns its own state (e.g. uniqStateOrDefaultState, sumStateOrDefaultState, uniqStateForEachState). #105085 (János Benjamin Antal).
• Fixed a bug in the Web UI (play.html): running a query while the cursor was past the only trailing ; reported "empty query" instead of running the query. #105107 (Alexey Milovidov).
• Fix LOGICAL_ERROR: 'No user in current context, it's a bug' when a CREATE TABLE ... AS SELECT inside a Replicated database reads from system.current_roles or system.enabled_roles. The query now succeeds and returns an empty result set in this internal DDL worker context. #105150 (Groene AI).
• Fixed ILLEGAL_TYPE_OF_ARGUMENT when merging quantileExactWeightedInterpolated, quantileDD, or quantilePrometheusHistogram aggregate states with their plural quantilesXxxMerge counterparts (and vice versa). The singular and plural variants of these three quantile families share the same internal aggregate state but were not listed in the internal name-mapping table, so cross-function state merge — and the function-fusion optimization for these families — were rejected. #105189 (Groene AI).
• Fix incorrect results of toStartOfWeek, toLastDayOfWeek, toMonday, toStartOfMonth, toLastDayOfMonth, toStartOfQuarter and toStartOfYear for Date32 and DateTime64 arguments whose result falls outside the Date range: instead of overflowing into arbitrary dates, results before 1970-01-01 are now clamped to 1970-01-01 and results after 2149-06-06 are clamped to 2149-06-06. This also fixes wrong query results (incorrectly pruned parts and granules) when such functions were used in WHERE over a Date32 or DateTime64 key containing out-of-range values. #105244 (Yarik Briukhovetskyi).
• Fix a logical error in arrayRemove when the first argument is an array of Variant whose alternatives are all incompatible with the type of the second argument and variant_throw_on_type_mismatch is disabled. The function now treats the comparison as "never equal" and returns the array unchanged instead of triggering a server-side assertTypeEquality failure. #105248 (Groene AI).
• Query can be executed successfully even if FileCache fails to create some directory on disk for caching. #105250 (Den Kalantaevskii).
• Fix server abort with Assertion 'px != 0' failed in ExtremesTransform when a query with extremes = 1 hits an exception (for example MEMORY_LIMIT_EXCEEDED) while the transform is building its extremes columns from the first chunk. The client now receives the original exception instead of crashing the server. #105264 (Groene AI).
• LEFT ANTI JOIN now correctly returns the right-side join key column with default values for unmatched rows, instead of duplicating the left key value. Previously, SELECT a.x AS l, b.x AS r FROM a LEFT ANTI JOIN b ON a.x = b.x could return r = a.x for the unmatched rows when it should return the default (0 for Int32, '' for String, NULL for Nullable). Only the join key column was affected; non-key right columns were already defaulted correctly. The same bug appeared in RIGHT ANTI JOIN whenever the optimizer swapped sides. Closes #99959. #105278 (Groene AI).
• Fix data loss in clickhouse-local when started repeatedly with a non-default --default_database (for example clickhouse-local --path X -- --default_database=mydb): the lookup for the persisted database UUID was hardcoded to metadata/default, so each restart minted a fresh UUID and the previous run's tables became invisible. Closes #101831. #105284 (Groene AI).
• Fix a logical error Mutation of Memory table produced incomplete output raised when running ALTER TABLE <memory_table> APPLY PATCHES or ALTER TABLE <memory_table> APPLY DELETED MASK. Memory tables do not own patch parts or deletion masks, so both commands are now correctly treated as no-ops. #105286 (Groene AI).
• Fix long-running queries with Unity Catalog by passing a table_id parameter in the query request. #105303 (Konstantin Vedernikov).
• Fix CANNOT_CONVERT_TYPE for Merge over Merge over Distributed with distributed_group_by_no_merge=1. #105330 (Azat Khuzhin).
• Fix clickhouse local and clickhouse client silently ignoring --query/-q when a positional file argument was also given. Both forms now produce BAD_ARGUMENTS consistently. #105334 (Raúl Marín).
• Fix REPLACE TEMPORARY TABLE silently creating a new table when the target didn't exist. It now throws UNKNOWN_TABLE, matching REPLACE TABLE semantics. Use CREATE OR REPLACE TEMPORARY TABLE to keep the create-or-replace behavior. #105373 (Groene AI).
• Fixed long-running reads (e.g. INSERT ... SELECT) from a DataLakeCatalog database with catalog_type = 'glue' failing with an ExpiredToken error once the STS session credentials captured at table-metadata load time crossed their expiry. The AWS STS credentials are now refreshed mid-query, so such reads continue past the token's expiry. #105381 (Pratima Patel).
• Fix logical error in negative LIMIT BY in some cases when used with ARRAY JOIN. #105403 (Nihal Z. Miaji).
• Fix inflated read_bytes (and the derived bytes/s shown in system.query_log, progress bar, etc.) when reading Parquet files. The previous implementation reported the row group's total compressed size on every chunk, so reading K of N columns overcounted by N / K. It is now summed only across the selected columns. Also fixes file-level progress tracking for Iceberg tables, which previously never reported the data file size. #105413 (Groene AI).
• Fixed a possible server segfault in cluster table functions (s3Cluster, urlCluster, fileCluster, ...) when the planner produces a SELECT with the recursive_with flag set but no WITH expression. Closes #105370. #105433 (Groene AI).
• Fix wrong result of countDistinct / uniqExact on Nullable columns when count_distinct_optimization = 1 (the NULL group was incorrectly counted). #105439 (Raúl Marín).
• Fixed a heap-buffer-overflow when reading Arrow or ArrowStream files with corrupted intermediate offsets in a binary or string column, and a null-pointer dereference when reading geo-tagged Arrow columns. #105449 (Raúl Marín).
• Validate Dynamic/Variant types in window PARTITION BY, it was not checked before when allow_suspicious_types_in_group_by is disabled. Closes #105028. #105450 (Pavel Kruglov).
• Fix input_format_json_empty_as_default not working in JSONStrings* formats. Closes #104913. #105453 (Pavel Kruglov).
• Fix NULL insert into Variant column via VALUES format during expression parsing. Closes #104909. #105455 (Pavel Kruglov).
• Fix dictGetOrDefault throwing CANNOT_INSERT_NULL_IN_ORDINARY_COLUMN when the default argument is a Nullable expression and short_circuit_function_evaluation is enabled with a mix of found and not-found dictionary keys. #105461 (Raúl Marín).
• Fix silent value truncation in Dynamic columns when the Quoted (Values) text reader falls back to String for incomplete inferred types like Map(Array(Nothing), ...). Previously the fallback wrapped the raw field with naive '...' concatenation, so an inner single quote (always present for such fallbacks) prematurely terminated the quoted string and the rest of the value was lost. #105463 (Groene AI).
• Fix SIGSEGV when reading Dynamic subcolumns from compressed Memory table after ALTER. Closes #104901. #105464 (Pavel Kruglov).
• Fix toFloat64/toUInt32/toString/etc. on Dynamic ignoring cast_keep_nullable. Closes #104789. #105467 (Pavel Kruglov).
• Include skip_first_lines in schema cache key for WithNames formats. Closes #104527. #105469 (Pavel Kruglov).
• Fix a server segfault in uniqStateOrNull / uniqStateOrDefault / uniqOrNullState (and similar combinator chains over uniq) when used with GROUP BY ... WITH ROLLUP, WITH CUBE, or WITH TOTALS and a Nullable argument. #105470 (Groene AI).
• Fix NOT_FOUND_COLUMN_IN_BLOCK exception when combining ORDER BY ... WITH FILL INTERPOLATE and LIMIT N BY with the analyzer enabled. Closes #103474. #105481 (Yakov Olkhovskiy).
• Fix toStartOfMillisecond and toStartOfMicrosecond returning a result off by nearly a second for negative (pre-epoch) DateTime64 values, and fix UndefinedBehaviorSanitizer signed-integer-overflow in toStartOfSecond, toStartOfMillisecond, and toStartOfMicrosecond for DateTime64 inputs near INT64_MIN. #105482 (Groene AI).
• Add a new compatibility setting analyzer_compatibility_prefer_alias_over_subcolumn (disabled by default). When enabled, the new analyzer prefers the alias-prefix interpretation over Tuple-subcolumn / dotted-column matches for multi-part identifiers, restoring the previous interpreter's behavior. This avoids AMBIGUOUS_IDENTIFIER (and related) errors when a query joins a table whose name matches an inner table of a CTE/subquery that uses SELECT * over a join, where asterisk-renamed columns (e.g. b.id) would otherwise leak the inner table identifiers into the outer scope. #105491 (Vladimir Cherkasov).
• A vector search query executed with the index only optimization now returns the correct value for L2Distance() if it is in the SELECT list. The function was incorrectly returning the L2-squared distance value. Note that the vector search query was returning the correctly ranked results, only applications explicitly retrieving and interpreting the L2Distance() value would have seen the squared value. #105495 (Shankar Iyer).
• Fixed a rare issue in new Kafka table engine where messages could be incorrectly handled during topic partition reassignment, potentially leading to skipped messages after offset rollback. #105500 (János Benjamin Antal).
• Fix an exception (Trying to execute PLACEHOLDER action logical error) when a MATERIALIZED CTE whose body is a correlated subquery is used as the right-hand side of IN. Such a CTE is now rejected at analysis time, consistent with how the same pattern is already rejected when the CTE is referenced directly in FROM. #105518 (Groene AI).
• Fix stdout/stdin compression not applied when format is explicitly specified. Closes #104441. #105528 (Pavel Kruglov).
• Fix SEGFAULT in singleValueOrNull deserialization for JSON type. Closes #103630. #105535 (Pavel Kruglov).
• Fix clickhouse-format --backslash silently dropping INSERT VALUES data. Closes #103533. #105536 (Pavel Kruglov).
• Fix variant_throw_on_type_mismatch/dynamic_throw_on_type_mismatch=false not catching exceptions during function execution. Closes #103484. #105543 (Pavel Kruglov).
• Fix ignoring input_format_try_infer_datetimes during insertion into shared data in JSON. Closes #103221. #105544 (Pavel Kruglov).
• Fix histogram producing wrong results for small unsorted inputs. Closes #103109. #105548 (Pavel Kruglov).
• Fix DateTime wrapping around for out-of-range values in JSONExtract and text deserializations. Closes #103094. #105551 (Pavel Kruglov).
• Fix usage of insertion table in table functions when optimize_trivial_insert_select is enabled. Closes #103083. #105555 (Pavel Kruglov).
• Fix CASE expression returning the ELSE branch instead of the matching THEN when both the expression and a WHEN value were NULL. #105556 (Raúl Marín).
• Fixed a crash in replxx caused by hitting the FD_SETSIZE limitation of select (now replaced with poll). Previously, with SSH or the web terminal enabled, this could crash the server. #105559 (Azat Khuzhin).
• Materialize subcolumns in executePartitionByExpression before executing expression. Closes #103057. #105573 (Pavel Kruglov).
• Fix NOT_FOUND_COLUMN_IN_BLOCK exception when TTL expression references a subcolumn. #105578 (Pavel Kruglov).
• Fix a server crash (SIGSEGV) reachable by any user with CREATE TABLE rights when sending CREATE TABLE ... TO INNER UUID '...' without an ENGINE clause over HTTP or the native protocol. The same bug also crashed the client. The parser now reports a proper BAD_ARGUMENTS error instead of dereferencing a null pointer. #105579 (Groene AI).
• Fix estimateCompressionRatio window function losing accumulated data between rows. Closes #101738. #105581 (Pavel Kruglov).
• Fix crash when inserting tuples of different sizes in the same VALUES clause into a String column. Closes #101727. #105582 (Pavel Kruglov).
• Hive partition value extraction now honors the cast_string_to_date_time_mode setting and accepts ISO 8601 timestamps with timezone suffixes (e.g. +0000, +00:00, Z) in partition keys by default. #105584 (Alexey Milovidov).
• Fixes NOT_IMPLEMENTED error on toString from DateTime with Timezone containing NULL value. Closes #103712. #105587 (Yarik Briukhovetskyi).
• Fix OOB read in flattened Dynamic column Native deserialization. #105666 (Pavel Kruglov).
• Fix a LOGICAL_ERROR (Unexpected return type from if) raised during query planning for if expressions whose result type is Variant and whose second-or-third branch is a constant-condition if over a UInt64 literal that fits into Int64. Closes #105649. #105680 (Groene AI).
• Fix wrong results when reading an Iceberg table with iceberg_use_version_hint = 1 after another writer (such as the icebergLocal/icebergS3 table function) without the setting advances the table. version-hint.text is now kept in sync by every writer once the file exists, so subsequent readers using the hint see the latest snapshot. #105682 (Groene AI).
• Fixed a silent under-count in SELECT queries when use_query_condition_cache = 1 (default). A query of the shape PREWHERE pk_prefix = X WHERE non_pk IN (...) against a column with a bloom-filter skip index poisoned the QueryConditionCache for the pk_prefix = X predicate, so a subsequent benign SELECT count() ... WHERE pk_prefix = X returned an incorrect, under-counted result. Affected all 26.x releases. #104781. #105686 (Groene AI).
• Fixed singleValueOrNullMerge returning a concrete value instead of NULL when merging a state that had already observed multiple distinct values. #105734 (Minh Vu).
• Fix Template input format error recovery after malformed rows. #105735 (Yue Ni).
• Fix a crash in the mongodb table function, MongoDB storage and MongoDB dictionary source when the collection name is empty or contains NUL bytes. #105776 (Raúl Marín).
• Fix Keeper snapshot cleanup after failed writes so partial snapshots are cleaned up safely and failed writes can be retried without advancing latest_snapshot_meta. #105779 (Antonio Andelic).
• Fix ALTER TABLE ... CLEAR COLUMN being rejected for explicit SummingMergeTree and CoalescingMergeTree columns_to_sum columns. #105785 (Antonio Andelic).
• Fixed an assertion in DatabaseCatalog::tryGetDatabase (and resulting UNKNOWN_DATABASE error in release builds) when creating a parameterized view whose database name is supplied via a query parameter, for example CREATE VIEW {db:Identifier}.v AS SELECT {p:UInt64}. Parameters in the DDL parts of the CREATE statement are now substituted at create time, while parameters in the SELECT body remain available for substitution at view-call time. #105799 (Groene AI).
• Fix Bad get: has Decimal32, requested Decimal128 from sumMap and sumMapWithOverflow over a Nested(... Nullable(Decimal(P, S))) column when the aggregate state is serialised (e.g. parallel replicas, sumMapState via a binary-state formatter, external aggregation). #105816 (Groene AI).
• Fix Expected ColumnLowCardinality, got String / Bad cast from type DB::ColumnString to DB::ColumnLowCardinality errors when apply_mutations_on_fly = 1 is used on a table with pending on-fly UPDATE/DELETE mutations queued before an ALTER MODIFY COLUMN ... LowCardinality(...) mutation. #105847 (Raúl Marín).
• Iceberg writes now preserve NULL values in Nullable(T) partition columns. Previously, a NULL written by ClickHouse showed up as the default value of the inner type (0 for int) when read back by Spark or other Iceberg readers. Closes #105852. #105862 (Groene AI).
• Fixed Parquet and ORC filter pushdown for IN (subquery) predicates, allowing row-group/page/bloom-filter pruning to work for file, url, s3, and object-storage reads. #105863 (Arsen Muk).
• Fix read-in-order for Merge tables (with a new analyzer). #105867 (Nikolai Kochetov).
• Fixed Iceberg v2 merge-on-read position deletes returning wrong rows when a single delete file references multiple data files and several such delete files apply to the same data file. The streaming reader (use_roaring_bitmap_iceberg_positional_deletes = 0) now filters delete-file rows by file_path in C++ instead of relying on Parquet row-group pruning, restoring the ascending-positions invariant. #105888 (Groene AI).
• Fix Cannot find column error for distributed queries with IN Array(...) filter for the new analyzer. #105894 (Nikolai Kochetov).
• Fix a SIGSEGV in ALTER TABLE ... MODIFY COLUMN ... Nullable(...) on MergeTree tables when a column with STATISTICS is concurrently dropped by another ALTER. Closes #105912. #105917 (Groene AI).
• Fixed a server crash that could occur when a query reading from PostgreSQL — via the postgresql table function, the PostgreSQL table engine, or a dictionary with a PostgreSQL source — was cancelled (for example with KILL QUERY) and cancelling the remote PostgreSQL query failed. #105949 (Rory Shanks).
• Fix SYSTEM INSTRUMENT ADD formatting so handler arguments are separated by a single space, and reject invalid SLEEP instrumentation argument lists with more than two values or a range where the minimum is greater than the maximum. #105984 (Pablo Marcos).
• Fix possibly wrong results for queries that combine an outer join with a subsequent inner join referencing the outer join's null-supplying side. Join reordering could pick a plan that pulled inner-join conditions into the outer join's ON clause. #105992 (Vladimir Cherkasov).
• Fixed a possible crash due to a too-large string literal sent within the query. #105996 (Nikita Taranov).
• Fix INVALID_WITH_FILL_EXPRESSION exception when using INTERPOLATE () (empty) with a sorting prefix in ORDER BY and use_with_fill_by_sorting_prefix enabled. Sorting prefix columns are now correctly excluded from the implicit interpolation set, matching the behavior of explicitly named INTERPOLATE (col). #106001 (Yakov Olkhovskiy).
• Fix ALTER TABLE partition operations silently failing for Bool partition keys. Closes #101722. #106004 (Pavel Kruglov).
• Fix JSONExtractRaw and JSONHas for typed JSON paths with default values. Closes #101721. #106005 (Pavel Kruglov).
• Fix incorrect '/'-prefix addition on empty basepaths in data lake configurations. Closes #105989. #106013 (thewisenerd).
• Fix IcebergLocal table engine becoming read-only after a DETACH + ATTACH cycle or a server restart, which made every subsequent INSERT fail with Local object storage Local is readonly. (READONLY). #106016 (Groene AI).
• Fix Keeper failures during follower catch-up when the new request dispatcher response queue could fill before the response thread started. #106049 (Antonio Andelic).
• Better compatibility with the old analyzer. If the table has columns like x.a Array, x.b Array, x String, prefer arrays for ARRAY JOIN x. #106069 (Nikolai Kochetov).
• Fixed the filesystem cache being silently disabled for Azure Blob Storage (e.g. Delta Lake tables over Azure) because object metadata did not include the blob ETag. #106091 (thewisenerd).
• Fix system.dictionaries returning 0 rows with partial SHOW DICTIONARIES revoke. #106105 (Pavel Kruglov).
• Fixed a server crash when querying DeltaLake tables with allow_experimental_delta_kernel_rs enabled and a credential or option that contained invalid bytes (the Rust FFI panicked across the extern "C" boundary). #106109 (Raúl Marín).
• Fix incorrect results for queries against tables whose ORDER BY contains a monotonically decreasing function such as (c0 / -42) or intDiv(c0, -42). Predicates on the underlying column (for example, c0 < 0) could wrongly prune granules that contained matching rows, producing missing results. Closes #106084. Closes #106124. Closes #106080. #106136 (Nihal Z. Miaji).
• Fix support for using WASM SQL UDFs in MATERIALIZED VIEW definitions. #106161 (Yue Ni).
• Iceberg partition pruning now correctly handles WHERE partition_col = (SELECT ... FROM ...) filters where the analyzer wraps the scalar subquery result in an internal _CAST(Const, 'TargetType') with matching source and target types. Previously such filters disabled partition pruning and triggered a full table scan. #106204 (Groene AI).
• Fix clickhouse local's --query_id parameter to allow it to specify custom query id. #106205 (Yue Ni).
• Fixed the S3 storage class (s3_storage_class / s3_storage_class_name) being ignored for objects written via multipart upload on S3 disks and object storage, which caused large objects to be created with the default STANDARD class. The option name is now accepted both as s3_storage_class and s3_storage_class_name for disks, object storage and backups. #106214 (Alexey Milovidov).
• Fixed Keeper sometimes getting stuck on startup when setting nuraft_max_log_gap_in_stream is set to non-default value (default is 0, i.e. disable pipelining of append_entries requests). #106220 (Michael Kolupaev).
• Validate corrupted DDSketch aggregate-function state (bin keys) on insertion instead of accepting malformed data. #106236 (Yarik Briukhovetskyi).
• Fixed coordinator mode mismatch when subqueries override in-order settings. #106243 (Nikita Taranov).
• Fix optimize_skip_unused_shards did not apply (and force_optimize_skip_unused_shards falsely failing) when a Distributed table is queried through a Merge table or the merge table function, with the predicate applied above it. #106250 (Nikolai Kochetov).
• Fix INTERPOLATE () throwing INVALID_WITH_FILL_EXPRESSION when ORDER BY columns are aliased in the SELECT list with the old analyzer. Closes #106248. #106252 (Yakov Olkhovskiy).
• Fixed an abort when deserialising a malformed AggregateFunction(uniqTheta, ...) state from RowBinary input or a query parameter. The bad input is now rejected with CORRUPTED_DATA instead of escaping as a std::exception and aborting the process via abortOnFailedAssertion. #106260 (Groene AI).
• Reject out-of-range IntervalKind bytes during RowBinaryWithNamesAndTypes type decoding (input_format_binary_decode_types_in_binary_format = 1) with a clear INCORRECT_DATA error instead of constructing a DataTypeInterval with an invalid kind that could subsequently trip undefined behavior in hash paths. #106261 (Groene AI).
• Fix SLRU downgrade failure rollback issue in 26.1+. Fix System/Data cache split priority with keep_free_space_ratio feature. #106286 (Kseniia Sumarokova).
• Read the null subcolumn as a JSON path in Nullable(JSON) instead of the null-map. Closes #106085. #106295 (Pavel Kruglov).
• Fix RestCatalog::empty returning the wrong result when an Iceberg REST catalog contains tables. #106301 (Lefteris).
• Fixed an exception for INNER JOIN queries with an empty left MergeTree table when enable_parallel_replicas, query_plan_use_new_logical_join_step, and query_plan_optimize_join_order_algorithm = 'greedy' are enabled. #106338 (Nikolai Kochetov).
• Fixed an incorrect conversion of subnormal Float16 values to Float32 (e.g. when reading them from Numpy .npy files), caused by an off-by-one mantissa shift. #106343 (Joanna Hulboj).
• Fix a crash and a possible NOT_FOUND_COLUMN_IN_BLOCK error when constraint-based optimization (optimize_using_constraints) is used with correlated subqueries. #106349 (Raúl Marín).
• Fixed an out-of-bounds read in sipHash64Keyed, sipHash128Keyed and sipHash128ReferenceKeyed when hashing a column whose arrays are all empty and the key is not constant. #106355 (Raúl Marín).
• Fixed SYSTEM RELOAD CONFIG discarding per-endpoint Azure Blob Storage settings (such as use_native_copy), which caused a disk's configured settings to be ignored for BACKUP/RESTORE until the server was restarted. #106357 (Julia Kartseva).
• Fix regexpExtract(haystack, pattern) so that patterns without a capturing group return the whole match instead of throwing INDEX_OF_POSITIONAL_ARGUMENT_IS_OUT_OF_RANGE. #106374 (Groene AI).
• Fix LOGICAL_ERROR exception during cache predownload when a remote S3 object is overwritten with shorter content between listing and reading. #106375 (Nikita Fomichev).
• Fix memory usage growth in filesystem cache. #106387 (Kseniia Sumarokova).
• Fix multiple heap out-of-bounds reads in the Arrow IPC format reader (ArrowColumnToCHColumn). A malformed Arrow file could declare more rows than its buffers contain, declare list/struct/map child lengths inconsistent with their parent, supply non-monotonic list offsets, or truncate a child validity bitmap, causing reads past the end of heap allocations. This is reachable by any user with SELECT privilege via file(), format(), table functions, or ArrowFlight inputs. All data, offsets, view-struct, and validity-bitmap buffers are now validated before any raw pointer access, and list/struct/map shapes and offsets are checked for consistency. #106395 (Raúl Marín).
• Fixed backups failing with FILE_DOESNT_EXIST when a refreshable materialized view's REPLACE target is collected on a Replicated or Shared database whose materialized view isn't yet instantiated on the backup-initiating replica. #106411 (Julia Kartseva).
• Fix a logical error Column identifier ... is already registered when a mutation (DELETE/UPDATE) predicate contains an IN/EXISTS subquery that reads from a default table expression nested in another subquery. #106414 (Alexey Milovidov).
• Fix a logical error (Left and right columns have same names) in the join order optimizer that could occur for joins executed with parallel replicas when two relations in the join graph share column names. #106418 (Alexey Milovidov).
• Fix a logical error when building a polygon dictionary from source data containing NaN or infinite point coordinates. Such coordinates are now rejected with a clear error. #106423 (Alexey Milovidov).
• Fixed a bug where the used_privileges and missing_privileges columns of system.query_log could contain privilege strings leaked from unrelated earlier queries of a different user, database, or session. #106425 (Alexey Milovidov).
• Functions base58Encode, base58Decode and tryBase58Decode now respect max_execution_time and query cancellation on large inputs, and reject inputs larger than 10 KB instead of running for a very long time. The limit is configurable via the new setting function_base58_max_input_size (0 disables it). #106428 (Alexey Milovidov).
• Fix sporadic incorrect results for ORDER BY ... DESC queries when reading wide parts in reverse order with read_in_order_use_virtual_row_per_block = 1 and a small max_block_size. #106429 (Vladimir Cherkasov).
• Fixed a NOT_FOUND_COLUMN_IN_BLOCK exception when querying an Iceberg or S3 table with a compound WHERE containing IS NOT NULL on a column that is not in the SELECT list, using the Parquet V3 native reader. #106443 (Shaohua Wang).
• Allows user to specify headers for HTTPDictionary using named collections. #106459 (Jan Rada).
• Fix a case where a worker thread could stay attached to a stale thread group after CurrentThread::attachToGroup failed part way through, causing later tasks on the same thread to fail with Thread is already attached to a group. #106462 (Mikhail f. Shiryaev).
• Fixed an exception when a vector search query uses a vector index and uses another skip index like minmax and use_skip_indexes_on_data_read = 1. #106473 (Shankar Iyer).
• Malformed Avro enum values are now validated and rejected with an error instead of causing an out-of-bounds read and abort when deserializing corrupted Avro data. #106476 (Miсhael Stetsyuk).
• Fix inflated progress reporting when reading from Iceberg tables with _file or _path filters. Previously, total_bytes_to_read progress included all files from the manifest regardless of filtering. #106491 (Pedro Ferreira).
• Fixed a Bad cast exception for Redis dictionaries that use STORAGE_TYPE 'simple' with a cache/direct layout and a single string (complex) key; such dictionaries now work, and composite keys over simple storage report a clear error. #106501 (Vladimir Cherkasov).
• Fix wrong-results bug where WHERE c0 = const returned no rows for tables with ORDER BY f(c0) when f(const) evaluates to NaN, e.g. ORDER BY sqrt(c0) with a negative constant. The primary-key analysis incorrectly pruned every granule and poisoned the query condition cache for subsequent queries. #106507 (Groene AI).
• Fix LIMIT WITH TIES and fractional LIMIT WITH TIES not respecting the collation from ORDER BY ... COLLATE when determining ties. Rows that are equal according to the collation (for example '1' and '01' under numeric collation) were compared byte-wise, so some tied rows were wrongly dropped from the result. #106539 (Nihal Z. Miaji).
• Fix DISTINCT in order and LIMIT BY in order optimizations (including negative LIMIT BY) returning wrong results when the input is sorted with a collation (ORDER BY ... COLLATE). Rows that are equal according to the collation (for example 'a' and 'A' under a case-insensitive collation) are ordered by collation key and are not adjacent by value, so the in order optimization is now skipped when a collator is used. #106564 (Nihal Z. Miaji).
• Fixed wrong results for SELECT c, count() FROM t WHERE c GROUP BY c against tables with the implicit _minmax_count_projection, an explicit aggregate projection, or a normal projection: every group used to collapse into one row with a constant key and the total row count. #106590 (Groene AI).
• Fixes a bug where users could not use scalar subqueries in the first argument of IN where the second argument is a non-constant tuple. #106610 (Yarik Briukhovetskyi).
• Fix exception Mutation of Memory table produced incomplete output raised when running ALTER TABLE <memory_table> commands that have no per-row data effect on a Memory engine, namely APPLY PATCHES, APPLY DELETED MASK, MATERIALIZE STATISTICS, MATERIALIZE INDEX, MATERIALIZE PROJECTION, and REWRITE PARTS. Memory tables do not own those structures, so such commands are now treated as no-ops. #106621 (Groene AI).
• Fix session_timezone being ignored when serializing LowCardinality(DateTime) columns to text formats (CSV, TSV, JSONEachRow, etc.). Previously, after the first write of a LowCardinality(DateTime) column on a server, every subsequent query that wrote such a column rendered the wall-clock string in whichever timezone was first seen, regardless of session_timezone. #106634 (Groene AI).
• Fixed a LOGICAL_ERROR "Trying to get name of not a column: ExpressionList" raised by queries that pass an asterisk inside multiIf to a table function argument, e.g. numbers(multiIf(*, ...), 2). The query now rejects the unresolvable matcher with UNSUPPORTED_METHOD. #106647 (Groene AI).
• Fix server failing to start with Too many marks in file ...skp_idx_idx.cmrk4, marks expected 0 (bytes size 0) when a MergeTree table has a skip-index part with zero granules and a non-empty marks file on disk. #106675 (Groene AI).
• Reject pathological file glob patterns that would cause unbounded recursion in directory listing. A maximum recursion depth of 1000 is now enforced; queries that exceed it raise TOO_DEEP_RECURSION instead of crashing the server with a stack overflow. #106676 (Groene AI).
• Fix server abort Bad cast from type DB::ColumnNothing to DB::ColumnVector<char8_t> in FunctionIf::executeForConstAndNullableCondition when the if/multiIf condition constant-folds to Const(Nullable(Nothing)) (for example, an out-of-range subscript on an empty array, like arraySort(x -> x, [])[toNullable(1)]). #106678 (Groene AI).
• Fix exception 'Trying to read from input() twice.' raised when the table function input is wrapped in a non-MATERIALIZED CTE that is referenced from more than one place in the query. The query is now rejected with a clean INVALID_USAGE_OF_INPUT error at planning time. input is a one-shot client stream and can only be consumed by a single source in the query plan. #106682 (Groene AI).
• Make FORMAT apply to the EXPLAIN output of EXPLAIN ... INSERT ... SELECT ... FORMAT ... also when SETTINGS precede the FORMAT or the output format is Values. Follow-up to #101772. #106686 (Alexey Milovidov).
• Fixed a rare spurious RESOURCE_ACCESS_DENIED error ("Scheduler queue with resource request is about to be destructed") for a query that was actually granted access to a workload resource, caused by a reused thread-local request object retaining a previous request's failure. #106690 (Alexey Milovidov).
• Fix a race between destroying INATSConsumer objects and calling INATSConsumer::onMsg on them via callbacks in the NATS library. #106692 (Miсhael Stetsyuk).
• Fixed match, extract, extractAll and countMatches returning wrong results for regular expressions containing hex or octal escapes. #106709 (ofeliacode).
• Keeper's internal Raft TLS now honors the openSSL.client.verificationMode setting. Previously peer certificate verification was always enabled for inter-Keeper Raft communication regardless of this setting, so none was silently ignored. Now none explicitly disables Raft peer-certificate verification, while an absent setting keeps the previous secure-by-default behavior. Configurations that explicitly set none will stop verifying Raft peer certificates after upgrade, matching the configured intent. #106726 (Antonio Andelic).
• Fix logical error in startup scripts in SYSTEM RELOAD CONFIG. Additionally, load startup scripts on SYSTEM RELOAD CONFIG (currently private-only functionality). #106727 (Miсhael Stetsyuk).
• Revert a change that made sumMap / the -Map combinator reject custom-named numeric value types (such as SimpleAggregateFunction(sum, T) and Bool) with ILLEGAL_TYPE_OF_ARGUMENT: Values for -Map cannot be summed, breaking previously-working aggregations. #106729 (Nikita Fomichev).
• Fixed multiple memory-safety and resource-exhaustion issues in format readers reachable from untrusted input: a heap out-of-bounds read in the native Parquet reader's DataPageV2 definition/repetition level-length handling, a stack overflow on Parquet files with deeply nested schemas, and allocations that ignored max_memory_usage when parsing GeoParquet WKB/WKT geometry and Avro strings/bytes. #106739 (Raúl Marín).
• Fixed a heap buffer overflow (server crash) in decodeHTMLComponent when decoding strings containing the expanding HTML entities ≫⃒ or ≪⃒, reachable by any user with a single SELECT. #106741 (Raúl Marín).
• Reject CREATE TABLE, ALTER TABLE ADD INDEX, and CREATE INDEX with GRANULARITY 0 for skipping indexes with a clear BAD_ARGUMENTS error. Previously this triggered an Inconsistent AST formatting exception in debug builds. #106783 (Groene AI).
• Fixed Azure BACKUP/RESTORE ignoring endpoint settings for legacy-form azure_blob_storage disks. #106784 (Julia Kartseva).
• Fixed a Bad cast exception while pruning parts by MinMax statistics when a key column is LowCardinality and the predicate constant is LowCardinality(Nullable(...)). #106793 (Groene AI).
• Fix inconsistent columns (that leads to LOGICAL_ERROR later) on exception (i.e. MEMORY_LIMIT_EXCEEDED) during parsing. #106802 (Azat Khuzhin).
• Fix after configuring keeper_server.http_control.secure_port, the server returned an HTTP response when making requests to HTTPS clients. #106822 (linjiayu1025-collab).
• Fix logical error in parseDateTime with non-ASCII input bytes. #106856 (Pavel Kruglov).
• Fix SHOW CREATE ROW POLICY emitting restrictive/permissive in lowercase instead of uppercase, inconsistent with other keywords. #106865 (Valery Petrov).
• Fixes the case when parallel replicas wasn't applied for view with UNION due to empty table in the UNION. #106900 (Igor Nikonov).
• Fix server crash (SIGSEGV) when reading truncated Protobuf data with input_format_allow_errors_num > 0. #106905 (Andrey Tsarevskiy | Андрей Царевский ).
• Fix THERE_IS_NO_COLUMN exception for distributed queries involving optimize_rewrite_aggregate_function_with_if optimization when the aggregate function argument requires a cast to Nullable type. #106908 (Yakov Olkhovskiy).
• Fix an exception (LOGICAL_ERROR) in the join runtime filter when the join key contains a Variant or Dynamic type nested inside a Tuple, Array, or Map and the right side of the join has a single distinct value. #106931 (Groene AI).
• Fixed a signed integer overflow (undefined behavior) in arrayLevenshteinDistanceWeighted and arraySimilarity when the weight arrays contain large integer values. The weighted distance is now accumulated in a wide integer for integral weights, so large integer weights no longer overflow and stay exact. #106934 (Groene AI).
• Fix a server crash (null pointer dereference) when running TRUNCATE or DROP on an EmbeddedRocksDB table whose RocksDB handle was released, for example a read_only table whose data directory was emptied by a prior TRUNCATE. #106940 (Groene AI).
• Fix an exception (std::length_error reported as a LOGICAL_ERROR) when reading from a *Cluster table function such as urlCluster with a very large max_streams_for_files_processing_in_cluster_functions setting. The number of streams is now bounded to a sane value. #106946 (Groene AI).
• Fix a server crash (null pointer dereference of DB::IConnections) in RemoteQueryExecutor when a distributed query is cancelled right before it is sent to a shard. #106950 (Groene AI).
• Fixed elapsed_us always being zero, and read_rows/read_bytes being undercounted, in system.processors_profile_log and system.query_log for asynchronous insert flush (AsyncInsertFlush) queries. #106982 (Christoph Wurm).
• Fix a crash (Source column is not Map / SIGSEGV) when merging sorted blocks that contain a Variant column with a Map variant whose local storage order differs from its global order. #107011 (Groene AI).
• Fix a logical error conflicted_part_name.has_value() raised during a synchronous insert into a ReplicatedMergeTree table when the inserted block was fully deduplicated and the conflicting part's deduplication node had already been removed (for example by a concurrent DROP PARTITION). #107026 (Groene AI).
• Fixed an exception (logical error this->visited_views == right->visited_views) on INSERT when two materialized views on the same source table write to the same target table and a dependent view reads that target, with materialized_views_squash_parallel_inserts enabled. #107027 (Groene AI).
• Fixed a Block structure mismatch in UnionStep stream logical error (server abort on debug/sanitizer builds, Code: 49 on release builds) that occurred when one branch of a UNION/INTERSECT/EXCEPT read a Sparse-serialized column while the sibling branch read the same column as a full one (for example when pushing to a materialized view). #107041 (Groene AI).
• Fixed a LOGICAL_ERROR exception when inserting into a DeltaLake table with columns that do not match its write schema (for example a Nested column that flattens to subcolumns, or a table function with an explicit column subset). Such inserts now fail with a user-facing INCOMPATIBLE_COLUMNS error instead. Closes #87402. #107058 (Groene AI).
• Fix TYPE_MISMATCH error ("Cannot convert string ... to type ...") for ORDER BY <numeric column> ... LIMIT n queries when lazy materialization placed another column before the sort column. The top-K threshold is now read from the correct sort column. #107060 (Groene AI).
• Fixed a syntax error when a FORMAT, SETTINGS, or INTO OUTFILE clause follows SHOW ROW POLICIES or SHOW MASKING POLICIES (e.g. SHOW ROW POLICIES FORMAT TabSeparated). #107061 (Groene AI).
• Fix a compound ALTER TABLE ... RENAME COLUMN a TO b, RENAME COLUMN c TO a that reuses a freed column name (a "swap") between columns of different types. The materialized part recorded the wrong column type, so a later SELECT failed with Conversion between numeric types and IPv6 is not supported (or aborted on part load in debug builds). #107064 (Groene AI).
• Fixed non-deterministic results of the roundDown function when the boundaries array contains NaN. The same input value could return a finite boundary or NaN depending on the surrounding rows in a batch. NaN boundaries are now ignored, so the result depends only on the finite boundaries. #107065 (Groene AI).
• Fixed quantileTDigest and quantileTDigestWeighted throwing DECIMAL_OVERFLOW for Date and DateTime arguments when the interpolated quantile is fractional but in range (for example quantileTDigestWeighted(date, weight) on values that all fit in the type). The fractional result is now truncated to the result type, matching quantilesTDigestWeighted; genuine out-of-range values still raise an error. Closes: #106722. #107066 (Groene AI).
• Fix trimLeft, trimRight, and trimBoth (and aliases ltrim, rtrim, trim) throwing TOO_LARGE_STRING_SIZE when the custom trim character set is longer than 16 characters. Trim sets of any length are now supported again. #107071 (Nikita Fomichev).
• Fixed silent truncation of out-of-range integer values in Enum8/Enum16 type definitions. Enum8('a' = 200) now throws ARGUMENT_OUT_OF_BOUND instead of silently creating Enum8('a' = -56). #107081 (Groene AI).
• Fix wrong row order (and a LOGICAL_ERROR "Rows are not sorted with permutation" in debug builds) for multi-column ORDER BY ... LIMIT queries that sort by Nullable columns when several rows tie on the leading columns. #107094 (Groene AI).
• Fix a LOGICAL_ERROR (Expected the argument N to have X rows, but it has Y) when executing a function over a Dynamic column built by a JOIN over Dynamic (for example the non-joined rows of a RIGHT/FULL JOIN, or a correlated EXISTS subquery decorrelated into a join). #107095 (Groene AI).
• Fix spurious ZooKeeper session recreation on config reload. #107096 (Azat Khuzhin).
• Do not hold mutex across ZooKeeper reads in access entities refresh. #107097 (Azat Khuzhin).
• Fix a Logical error: Too large size passed to allocator exception on INSERT into a MergeTree table when adaptive_write_buffer_initial_size is set to an extremely large value. The adaptive write buffer initial size is now clamped to the buffer maximum. #107104 (Groene AI).
• Fix LOGICAL ERROR (Bad cast from type DB::ColumnString to DB::ColumnLowCardinality) when a Variant constant containing a LowCardinality member is compared to a key column whose key expression is a non-monotonic deterministic function (for example a minmax skip index over sipHash64(col)). #107111 (Groene AI).
• Fix a Bad cast from type DB::IColumn const* to DB::ColumnNullable const* logical error when a qualified asterisk (t.*) over a JOIN ... USING key is passed to an aggregate function and the other side of an outer JOIN has a Nullable key (with join_use_nulls = 0). #107129 (Groene AI).
• Fix ALTER TABLE ... ON CLUSTER batches that mix MODIFY SETTING/RESET SETTING with a comment change (for example MODIFY COMMENT 'x', MODIFY SETTING old_parts_lifetime = 123) being applied only on the leader replica, leaving the other replicas diverged. Also fix a positional or per-column-SETTINGS MODIFY COLUMN ... COMMENT being misclassified as a local comment-only metadata change, which left the column reorder out of the replicated metadata and could cause INCOMPATIBLE_COLUMNS on replica restart. #107142 (Groene AI).
• Fix a LOGICAL_ERROR ("Table expression ... data must be initialized") raised when a qualified asterisk matcher (for example x.*) referenced a recursive CTE by name inside its own recursive term. Such matchers now expand the recursive table's columns, the same way a qualified column (x.a) or an unqualified matcher (*) already does in that position. #107144 (Groene AI).
• Fixed wrong query results caused by the query condition cache when on-fly mutations (apply_mutations_on_fly) or patch parts filtered rows before PREWHERE. A query reading with apply_mutations_on_fly = 1 could poison the cache so that a later query with apply_mutations_on_fly = 0 and the same predicate skipped marks it should have read and returned too few rows. The same fix also covers row-level security policies, which are prepended as a filter ahead of PREWHERE: a query run under a restrictive row policy could poison the cache for a later query that uses the same predicate without that policy. #107145 (Groene AI).
• Fixed BACKUP to AzureBlobStorage: copying a data file inside a backup wrote the destination object outside the backup directory. Backup object existence checks on S3 destinations now use exact HeadObject requests instead of prefix listing, preventing false matches of similarly-prefixed keys. #107153 (Pablo Marcos).
• Fixed a signed integer overflow in quantileExactExclusive, quantilesExactExclusive, quantileExactInclusive and quantilesExactInclusive that could produce a wrong result for Int64 inputs spanning a large range. #107154 (Groene AI).
• Fixed a LOGICAL_ERROR ("Unexpected exception in refresh scheduling") that could put the server into a crash-loop on restart when a refreshable materialized view has a REFRESH ... DEPENDS ON <name> dependency whose unqualified name matches a temporary table or a CTE name. #107156 (Groene AI).
• Make sure we don't run startup scripts on config reload, as that is semantically wrong and unexpected by users - and has been known to be error-prone. #107187 (Miсhael Stetsyuk).
• Cap the max value for queue_size for pre-reserve. #107205 (Elian Gidoni).
• Fix the Argument ... of GROUPING function is not a part of GROUP BY clause error for queries that use the grouping function with the group_by_use_nulls setting enabled. #107206 (Nikolai Kochetov).
• Fix incorrect result order for ORDER BY over UNION ALL with optimize_read_in_order enabled when the union pipeline was narrowed due to max_streams_for_union_step settings; narrowing is now skipped when the plan relies on sorted UNION output streams. Closes #106880. #107208 (Vladimir Cherkasov).
• Fixed a possible null pointer dereference while resolving proxy configuration during late server shutdown. #107231 (Pedro Ferreira).
• Fix lightweight UPDATE queries with legacy parallel replicas enabled for non-replicated MergeTree tables. #107246 (Groene AI).
• Fixed a server abort (std::out_of_range logical error) when inserting into an Iceberg table whose write block column names do not match the field ids of the latest schema (for example after a concurrent writer renames a column within the iceberg_metadata_staleness_ms window). The insert now fails with a clean query error instead of crashing the server. #107279 (Groene AI).
• Fix the stuck shutdown bug on server and local due to static thread pools keeping idle threads indefinitely if max_*_thread_pool_free_size > 0. #107291 (Miсhael Stetsyuk).
• Fix the s3 table function silently ignoring a lowercase positional partition_strategy (e.g. hive). #107297 (Julia Kartseva).
• Fix low_cardinality_allow_in_native_format=0 handling in parallel blocks marshalling. #107319 (Azat Khuzhin).
• Fix wrong (often empty) results from ORDER BY <col> LIMIT n when the use_skip_indexes_for_top_k optimization is active and a part with a minmax skip index on the sort column has had rows removed by a lightweight DELETE. The optimization no longer ranks the stale minmax of lightweight-deleted parts ahead of the parts that hold the live top rows. #107320 (Groene AI).
• Fixed a bug in ClickHouse Keeper where the snapshot metadata reported via last_snapshot (and zk_latest_snapshot_size in mntr) could move backwards after a stale or duplicated snapshot install, which could also let a same-index local snapshot overwrite a registered snapshot file in place while it was still being streamed to a peer or uploaded to S3. #107321 (Antonio Andelic).
• Fixed possible server stack overflow (crash) when reading a deeply nested schema or value in the MsgPack, BSON, ORC, Parquet, JSON, DeltaLake, Iceberg and Paimon formats. Such deeply nested input is now rejected with an exception. #107341 (Raúl Marín).
• Fix a possible logical error in SYSTEM SYNC DATABASE REPLICA ... STRICT and make the STRICT modifier actually take effect for database replicas. #107344 (Pedro Ferreira).
• Fixes a server abort in debug/sanitizer builds when reading a DeltaLake table whose ClickHouse schema names a column that is absent from the Delta column mapping, for example after a column was renamed or dropped in the Delta log. The query now fails with a catchable INCORRECT_DATA error instead. #107347 (Groene AI).
• Fix ORDER BY ... WITH FILL producing extra rows when an ORDER BY column before the fill column uses a COLLATE collation. The rows are now grouped by the sorting prefix using that collation, matching the sort order. #107365 (Groene AI).
• Fixed a crash (LOGICAL_ERROR in debug builds) and a silent wrong-results bug (in release builds) when reading an Iceberg table whose metadata re-binds an existing schema-id to a different schema across metadata versions. Such metadata is now rejected with ICEBERG_SPECIFICATION_VIOLATION. #107370 (Groene AI).
• Fix a LOGICAL_ERROR (Variant N (T) has size X, but expected Y) when a function such as toString or concat is applied to a Variant or Dynamic column that holds a single non-empty variant together with NULLs, and the function returns its input column unchanged. #107374 (Groene AI).
• Fix Logical error: 'Duplicate announcement received for replica number N' that could occur with parallel replicas when a scalar subquery contained nested subqueries reading the same table. #107381 (Groene AI).
• Fix getServerSetting to return the live effective value for runtime-changeable server settings (such as max_server_memory_usage, mark_cache_size, max_concurrent_queries, thread pool sizes, etc.), matching what system.server_settings reports. #107388 (Alexey Milovidov).
• Fix arrayResize with a Decimal size argument: the size is now interpreted by its real value (e.g. arrayResize([1, 2, 3], 1.5::Decimal(2, 1)) returns one element) instead of the raw unscaled representation. #107389 (Alexey Milovidov).
• Fix a LOGICAL_ERROR (block.rows() == getRows()) raised on an async INSERT into an Alias table when use_strict_insert_block_limits was enabled. #107400 (Groene AI).
• Fix a logical error (Unexpected return type from equals. Expected Nullable(UInt8). Got UInt8) when the disjunction (partial predicate) push-down optimization pushes a condition over a USING key whose type is widened by the JOIN. Also fix a server crash (segmentation fault) in the analyzer when resolving identifiers in JOIN ... USING queries that contain constant-foldable if/multiIf branches referencing unknown identifiers. #107407 (Groene AI).
• Fixed a heap buffer overflow (server crash) in windowFunnel when finalizing a crafted aggregate-function state with an out-of-range event type, reachable by any user with a single SELECT. #107412 (uwezkhan).
• Fixed undefined behavior when a non-finite floating-point value (such as nan or inf) is passed as the timestamp/duration argument of the prometheusQuery / prometheusQueryRange table functions. Such an argument now raises BAD_ARGUMENTS instead of producing a garbage timestamp. #107417 (Groene AI).
• Fix MaterializedPostgreSQL silently stopping replication of changes when the PostgreSQL database or table name contains upper-case letters (the pgoutput consumer requested an unquoted, lower-cased publication name that did not match the case-preserving publication). #107423 (Alexey Milovidov).
• Fix an exception (Logical error: Not-ready Set is passed as the second argument for function 'in') when a key expression (ORDER BY, PRIMARY KEY, PARTITION BY, or a skip INDEX) contained an IN operator with a table on the right-hand side, e.g. ORDER BY (x IN some_table). Such key expressions are now rejected at table creation time. #107424 (Groene AI).
• Fix incorrect results from the optimize_rewrite_aggregate_function_with_if optimization for aggregate functions that preserve NULL payload values (the *_respect_nulls family: anyRespectNulls, first_value_respect_nulls, anyLast_respect_nulls, last_value_respect_nulls). The optimization no longer rewrites f(if(cond, x, NULL)) into the -If form for such functions. #107430 (Groene AI).
• Fix a spurious filesystem error: in last_write_time: No such file or directory exception when listing a local-disk object storage directory (e.g. an Iceberg table on a local disk) while files are being concurrently replaced. A concurrently removed entry is now omitted from the listing instead of aborting it. #107432 (Groene AI).
• Fix THERE_IS_NO_COLUMN error when optimize_if_transform_strings_to_enum = 1 and the optimized if/transform-over-string-literals expression is a GROUP BY or ORDER BY key over a Distributed table or parallel replicas. #107455 (Groene AI).
• Fixed a rare server crash in DISTINCT processing that could occur when an allocation failed (for example, when hitting a memory limit) while the set of distinct keys was being initialized. #107467 (Groene AI).
• Fix LOGICAL_ERROR: Unexpected return type from materialize (and similar type-mismatch errors) when apply_mutations_on_fly = 1 is used on a table with a pending on-fly UPDATE whose target column is also read as a function input by an earlier on-fly UPDATE, before an ALTER MODIFY COLUMN ... LowCardinality(...) mutation. #107475 (Groene AI).
• Fixed stale AWS STS credentials when reading DeltaLake tables over S3: the engine now keeps the freshly-credentialed S3 client when refreshing its snapshot, so long-running reads no longer fail after the STS token's TTL expires. The STS assume-role credentials provider now also honors credential refresh for any S3 access using STS. #107480 (Elmi Ahmadov).
• Fixed SELECT ... FINAL and OPTIMIZE TABLE ... FINAL returning duplicate rows after CREATE TABLE ... CLONE AS, ATTACH PARTITION ... FROM or MOVE PARTITION ... TO TABLE adopted parts from a plain MergeTree into a ReplacingMergeTree, SummingMergeTree or AggregatingMergeTree. The adopted part's merge level is now reset to 0 when the source and destination engines differ, so the destination deduplicates it on the next merge. #107481 (Groene AI).
• Fix an integer underflow in the PostgreSQL wire protocol parser where a message with a length field smaller than 4 caused a size - 4 wraparound and an oversized resize/ignore. #107485 (uwezkhan).
• Query cancellation is now better tracked while waiting for the quorum in ReplicatedMergeTree. #107513 (Nikita Taranov).
• Fixed a Not-ready Set is passed as the second argument for function 'in' (LOGICAL_ERROR) when querying a table with a PARTITION BY key and an IN/NOT IN subquery wrapped inside a larger expression, for example WHERE (c0 IN (SELECT ...)) != 0. #107515 (Groene AI).
• Fixed currentUser(), user(), SESSION_USER and authenticatedUser() evaluating to an empty string on the asynchronous insert flush path (with async_insert = 1). This affected DEFAULT/MATERIALIZED column expressions and materialized views that reference these functions, which silently stored an empty string instead of the inserting user. #107541 (Groene AI).
• With enable_analyzer = 1 (the default), querying a table by its bare name when it only exists in another database now suggests the right table, e.g. SELECT * FROM functions reports Maybe you meant system.functions?. Previously the new analyzer gave a hint-less Unknown table expression identifier error, while the old analyzer already produced the helpful suggestion. #107550 (Groene AI).
• Account memory used by the rapidjson library (in prettyPrintJSON, JSONMergePatch and the rapidjson JSON parser) against the memory tracker, so pathological inputs are rejected with MEMORY_LIMIT_EXCEEDED instead of allocating without bound. #107555 (Raúl Marín).
• Fix a LOGICAL_ERROR (updateFormatPrewhereInfo called more than once) raised when querying a file(), url(), or object-storage source with both an explicit PREWHERE and a WHERE while optimize_prewhere_after_pushdown was enabled. #107568 (Groene AI).
• Fix a crash (null pointer dereference) that could happen when a distributed query plan was executed locally (make_distributed_plan + distributed_plan_execute_locally) with log_formatted_queries = 1. #107570 (Groene AI).
• Fixed a server abort (std::terminate, signal 6) during teardown of a distributed-plan query (make_distributed_plan = 1) when a worker status-check failed to re-schedule the next check (for example CANNOT_SCHEDULE_TASK on shutdown or MEMORY_LIMIT_EXCEEDED). The query now fails cleanly and the server keeps running. #107575 (Groene AI).
• Added missing bounds checks in Elf and DWARF parsing. #107579 (Michael Kolupaev).
• Added missing bounds checks in ORC reader. #107580 (Michael Kolupaev).
• Fixed an exception (Digest does not match logical error) that could happen on RENAME TABLE, RENAME DATABASE, or CREATE OR REPLACE TABLE involving a TimeSeries table inside a Replicated database. Renaming a TimeSeries table is now supported. #107583 (Groene AI).
• Fix an unauthenticated memory-exhaustion denial of service on the MySQL protocol port. #107599 (Shaohua Wang).
• Fix DROP TABLE of a TimeSeries table in a Replicated database, which previously leaked the inner tables and left the background drop task retrying forever (DROP TABLE ... SYNC would hang). #107604 (Groene AI).
• Fixed two path-traversal issues in the replicated part fetch protocol that could let a malicious replica write files outside the part directory. #107606 (Antonio Andelic).
• Fixed 'Account must be specified error' when reading a Delta Lake table over Azure. #107620 (Smita Kulkarni).
• Fixed ALTER TABLE ... REPLACE PARTITION on a plain MergeTree table resurrecting the replaced-out parts after a server restart, which made the table return both the replacement rows and the stale replaced rows. #107623 (Groene AI).
• Fix a server crash when reading a materialized view whose target is a Distributed table while the query runs with enable_analyzer = 0. #107653 (Groene AI).
• When several quotas are assigned to the same user or role, all of them are now enforced together (a query is rejected if any of them is exceeded), instead of only one quota being enforced and chosen non-deterministically. SHOW QUOTA and system.quota_usage now show all quotas enforced for the current user. #107664 (Alexey Milovidov).
• Fixed s3 and other object storage table functions throwing LOGICAL_ERROR instead of BAD_ARGUMENTS when a key-value argument is duplicated, e.g. s3('http://...', format = 'CSV', format = 'TSV'). #107670 (Groene AI).
• Fixed the MySQL interface being unusable with MySQL Connector/J 8.2.0 and newer (including 9.x). The info field of the OK packet is now length-encoded, matching the MySQL server, so the JDBC driver can connect. #107693 (Alexey Milovidov).
• Fixed a LOGICAL_ERROR ("Input nodes size mismatch in dag") when a query with make_distributed_plan = 1 joins on a function-wrapped key whose two sides have no common type (for example ON intDiv(-1, t1.key) = t2.key with a UInt64 right key). #107701 (Groene AI).
• Reading Arrow/ArrowStream data with empty String/Binary columns produced by Apache Arrow Java < 19.0.0 (including Apache Spark) no longer throws INCORRECT_DATA. #107764 (Raúl Marín).
• Fixed a BAD_GET exception ("Bad get: has String, requested UInt64") from countmin column statistics estimation when a query compares a column against a literal of a different type that is not pre-coerced, such as numeric_col IN (SELECT '5') or string_col IN (SELECT 5). #107793 (Groene AI).
• Fixed the odbc and jdbc table functions hanging for minutes and ignoring query cancellation (KILL QUERY, max_execution_time) when the bridge becomes unresponsive while inferring the remote table structure. #107809 (Alexey Milovidov).
• Fixed an exception (Logical error: 'index >= result.start') when formatting a malformed query that mixes the positional and named secret-argument forms of the s3/gcs table functions, e.g. s3('url', 'a', 'b', secret_access_key = 'c'). #107818 (Groene AI).
• Fix set skip index not pruning granules over LowCardinality columns. #107868 (Konstantin Bogdanov).
• Fixed insert deduplication computing wrong hashes for String and Array columns with the server setting insert_deduplication_version = new_unified_hash: identical inserts could fail to deduplicate because the deduplication hash depended on the row's position within the inserted block. #107915 (Sema Checherinda).
• Fix incorrect results of ORDER BY over Nullable columns with multiple sort keys on macOS (Apple Silicon), caused by a missing sign-extension in the JIT-compiled sort comparator. #107973 (Raúl Marín).
• Fix performance regression when reading Dynamic columns with multiple threads. Caused by #100730. Closes #107942. #107997 (Pavel Kruglov).
• The deprecated data lake setting storage_catalog_url is now correctly rejected by the catalog guard (previously only storage_catalog_type and storage_aws_access_key_id were checked), and the error message lists all deprecated settings. #108040 (Alexey Milovidov).
• Fix a Bad cast from type DB::ColumnSparse to DB::ColumnVector<char8_t> logical error when a LIKE query reads from a text index via the direct-read fallback path over a column stored sparse. #108068 (Groene AI).
• Always run access cache batch-finished handlers, even on empty batch. #108124 (Azat Khuzhin).
• Fixed a LOGICAL_ERROR (Column identifier is already registered) for some queries with UNION ALL. #100770 (Shaohua Wang).
• Fixed a use-after-free of the workload storage mutex during server shutdown. #101447 (Tuan Pham Anh).
• Fixed a deadlock in ALTER DATABASE MODIFY COMMENT with the Shared catalog. #103683 (Nikolay Degterinsky).
• An empty Unicode-quoted identifier now raises a SYNTAX_ERROR instead of CANNOT_PARSE_QUOTED_STRING. #104173 (leonard9893).
• Preserve the original parameter types of timeSeries* aggregate functions so that AggregateFunction types round-trip correctly across table reattach and parallel replicas. #104812 (Vitaly Baranov).
• Fixed a LOGICAL_ERROR for a materialized CTE under serialize_query_plan with parallel replicas. #104896 (Igor Nikonov).
• Fixed signed integer overflow in the timeSeries*ToGrid functions when the staleness (window) parameter is near INT64_MAX. #105319 (Groene AI).
• A compatibility setting value no longer reverts apply_row_policy_after_final to false, so row policies are always applied correctly with FINAL. #105637 (Yarik Briukhovetskyi).
• Fixed clickhouse chdig client by honoring SETPGROUP/RESETIDS/SETSIGDEF in the posix_spawn stub. #105858 (Azat Khuzhin).
• Fixed an exception during merge-tree sanity checks on projections when the merge/mutate executor was not initialized. #105919 (Mikhail Artemenko).
• During index analysis on projections, the minmax index is now loaded from the projection itself rather than from the parent part, producing correct results. #105940 (Mikhail Artemenko).
• Fixed an exception in addMonotonicChain for materialize(monotonic_chain(...)). #106050 (Nikolai Kochetov).
• Fixed RESTORE failing on backups that include MASKING POLICY dependents. #106086 (Julia Kartseva).
• Fixed possible memory corruption when expanding SQL user-defined functions with prefer_column_name_to_alias enabled. #106121 (Nikolai Kochetov).
• A dictionary using the bridge connection is now reloaded after a server restart, re-establishing the connection. Closes #106151. #106152 (Pedro Ferreira).
• Fixed the filesystem cache for LocalObjectStorage. #106239 (Kseniia Sumarokova).
• Fixed the lazy remote source for table functions with use_delayed_remote_source. #106470 (Nikolay Degterinsky).
• Fixed timeSeriesLastToGrid for timestamps before the grid start and out-of-window timestamps. #106504 (Vitaly Baranov). #106577 (Vitaly Baranov).
• Fixed a LOGICAL_ERROR (Inconsistent AST formatting) on a function name containing query parameters. #106635 (Vitaly Baranov).
• Fixed a logical error when a table is dropped before distributed plan task deserialization. #106944 (Alexander Gololobov).
• Use exact comparison for Nullable GROUP BY keys. #107050 (Nikolai Kochetov).
• Fixed a LOGICAL_ERROR (Trying to get name of not a column) raised when a table-function argument was not a column expression (for example an unresolved * matcher from multiIf/CASE). #107411 (Alexey Milovidov).
• Fixed unbounded growth of the time-zone cache (DateLUT) when many distinct invalid time-zone names are processed. #107464 (Alexey Milovidov).
• Write the part_log entry before reporting a plain MergeTree mutation as done. #107741 (Azat Khuzhin).
• arrayFold now sanity-checks its array argument against malformed input. #107932 (Michael Kolupaev).
• Fixed a rare data race and possible use-after-free on the cached skip-index archive reader of a MergeTree part, which could happen when a query read skip indices while the part was being moved or renamed. #107995 (Raúl Marín).
• Fix performance regression for Map subcolumns with PREWHERE. #107988 (Pavel Kruglov).
• Fix parseDateTimeBestEffort with a timezone throwing CANNOT_PARSE_DATETIME on NULL rows of toString(Nullable(DateTime64)). #108310 (Yarik Briukhovetskyi).
• Fixed the ArrowFlight table function and engine rejecting a named collection that omits the optional dataset key with a No such key 'dataset' error. #108041 (Alexey Milovidov).
• Fixed an Inconsistent AST formatting logical error for a no-argument window function inside a CODEC or engine declaration (e.g. CODEC(cume_dist() OVER (...))); such a function now keeps its parentheses so the query survives a format/parse round-trip. #107806 (Alexey Milovidov).
• Fix hasToken with a separator-containing needle silently returning results via a text index instead of raising BAD_ARGUMENTS. #108189 (Jimmy Aguilar Mena).
• The setting use_skip_indexes_on_data_read can now be reverted to its pre-26.1 default (false) via the compatibility setting, providing an escape hatch for a performance regression where the on-data-read path defeats minmax/set/bloom_filter skip-index mark-range pruning. #108330 (egor romanov).
• Fixed a possible crash (null pointer dereference) when the database/db override of a named collection passed to remote/remoteSecure is not a constant database name, e.g. remote(nc, database = (SELECT 1)). The query now fails with a clear error instead of crashing. #108271 (Groene AI).
• Fixed refreshable materialized view getting stuck if the ZooKeeper connection is lost at the wrong moment. #108234 (Michael Kolupaev).
• Fix Bad cast from type DB::ColumnVector<...> to DB::ColumnTuple when reading an Array(Tuple(...)) column whose value is filled with defaults, e.g. after ALTER TABLE ... ADD COLUMN or after an unfinished ALTER TABLE ... CLEAR COLUMN mutation applied on the fly. #107232 (Groene AI).
• Fix a Bad cast from type DB::ColumnDynamic to DB::ColumnNullable logical error when an explicit reference to a JOIN ... USING key whose common supertype is Dynamic is passed to an aggregate function, for example count(t.key) IGNORE NULLS. #107289 (Groene AI).
• Fix silent data loss on plain (non-replicated) MergeTree when REPLACE PARTITION, MOVE PARTITION, DETACH PARTITION, or DETACH PART is run on a partition that still has unapplied lightweight UPDATE patches. These operations now reject the command, as ReplicatedMergeTree already does. #107386 (Groene AI).
• Fix a crash (SIGSEGV in release builds, type-mismatch assertion in debug builds) in has over a Map with a Dynamic key when the lookup argument is LowCardinality, e.g. has(map('a'::Dynamic, ...), toLowCardinality('b')). #107956 (Groene AI).
• Fixed a LOGICAL_ERROR ("Block structure mismatch ... between ConvertingTransform and RemovingReplicatedColumnsTransform") when inserting into a materialized view whose TO target table declares a column with a wider Enum than the view's SELECT produces. The valid Enum widening is now applied. #107648 (Groene AI).
• Fix NUMBER_OF_COLUMNS_DOESNT_MATCH error when querying a Distributed table (or using parallel replicas) that has several ALIAS columns expanding to the same expression and referencing them together with ORDER BY/GROUP BY/HAVING. #107913 (Yakov Olkhovskiy).
• Fixed undefined behavior (null pointer passed to memcpy) in the detectCharset and detectLanguageUnknown functions when the input string is larger than 32768 bytes and no character set can be detected. #108250 (Groene AI).
• Fix signed integer overflow (undefined behavior) in dateDiff with hour and minute units on extreme DateTime64 values close to the Int64 range limits. #108229 (Groene AI).
• Fix Too many marks for a text index on an empty merged part. #106867 (Azat Khuzhin).
• Fix a LOGICAL_ERROR ("Unexpected return type from if") when reading a column under apply_mutations_on_fly = 1 after an ALTER UPDATE col = ... WHERE <cond> with a non-constant or false condition followed by ALTER MODIFY COLUMN col <new type>. #108128 (Groene AI).
• Fix a server abort (Logical error in IColumn::insertFrom) when casting an Array(Dynamic) or Array(Variant) to QBit with accurateCastOrNull, e.g. accurateCastOrNull(CAST(range(114), 'Array(Dynamic)'), 'QBit(Float32, 114)'). #108288 (Groene AI).
• Fixed a syntax error when an alias follows a subquery in DESCRIBE TABLE (...) AS .... #100205 (Yarik Briukhovetskyi).
• getClientHTTPHeader is now correctly treated as non-deterministic, so its result is no longer incorrectly reused by the query result cache. #108029 (Alexey Milovidov).

Build/Testing/Packaging Improvement

• Build delta-kernel-rs with the default-engine-native-tls feature so that its own HTTP client (reqwest) can reuse the OpenSSL that ClickHouse already links in. This is only a partial native-tls enablement: object_store still forces reqwest/rustls-tls-native-roots, so reqwest ends up with both the native-tls and rustls backends. delta-kernel-rs remains disabled under MSan for now because ring is still compiled in via object_store (both transitively through rustls and directly for AWS request HMAC signing), and its hand-written assembly does not generate the symbols MSan requires (tracked upstream at arrow-rs-object-store#585). #96856 (Austin Bonander).
• Add PGO (Profile-Guided Optimization) and BOLT (Binary Optimization and Layout Tool) post-link optimization for the clickhouse binary. Profiles are collected from CI workloads and applied as a best-effort step during release builds — both stages fall back to non-optimized output if a profile is stale or incompatible. As of today, there are no benefits from PGO. #100938 (Alexey Milovidov).
• Add --storage mode to clickhouse keeper-bench that benchmarks KeeperStorage in-process (no network, no raft, no state machine), using the same setup/generator config sections as the network mode. #103081 (Michael Kolupaev).
• Fix build with ENABLE_AWS_S3=OFF. #105390 (Yue Ni).
• Update mongo-cxx-driver to r4.3.0. #105522 (Konstantin Bogdanov).
• Fix build against RapidJSON. #105674 (Ilya Golshtein).
• Speed up the build by removing transitive includes from widely-used base/ headers and stripping unused code from the vendored Poco/Logger.h. #105702 (Raúl Marín).
• Updated libxml2 from 2.15.1 to 2.15.3. #105985 (Konstantin Bogdanov).
• Use expat 2.8.1 inside Poco. #105988 (Konstantin Bogdanov).
• Bump thrift to v0.23.0. #105993 (Konstantin Bogdanov).
• Use postgres tag REL_18_4. #105994 (Konstantin Bogdanov).
• Upgrade krb5 to 1.22.2. #106076 (Konstantin Bogdanov).
• Update bundled curl to 8.20.0. #106077 (Konstantin Bogdanov).
• Bumped mariadb-connector-c to 3.1.29. All the ClickHouse-relevant patches preserved. #106287 (Nikita Mikhaylov).
• Bump distroless base image digests for libssl3t64 CVE fixes. #106360 (Rahul Nair).
• Use wasmtime v45.0.1. #106836 (Konstantin Bogdanov).
• Bump openssl to 3.5.7. #106844 (Konstantin Bogdanov).
• Distroless Docker build now also updates the :X.Y-distroless and :X.Y.Z-distroless floating tags, not just the full-version tag. #106932 (Rahul Nair).
• Disable unused curl features, such as NTLM auth, cookies, alt-svc, HSTS, DNS-over-HTTPS, netrc, MIME, AWS SigV4. #107226 (Konstantin Bogdanov).
• Updated NuRaft with a fix for a snapshot-install livelock that occurred when snapshot IO ran on a background thread. The nuraft_use_bg_thread_for_snapshot_io Keeper setting remains disabled by default; CI now randomizes it to cover both modes. #107338 (Antonio Andelic).
• Fix building abseil when the ClickHouse checkout path contains a substring matching a header extension. #107349 (zhiqiang).
• Determine the L2 cache size from CPUID on x86_64 instead of the glibc-specific sysconf(_SC_LEVEL2_CACHE_SIZE), which is not available under musl libc. #107469 (Konstantin Bogdanov).
• Increase the stack size for musl builds to 8 MiB to support deeply-nested queries. #107470 (Konstantin Bogdanov).
• Derive the set of C library symbols localized in Rust static libraries from the actual reference libraries instead of a hand-maintained allowlist, so all compiler-rt builtins and platform libm functions are covered. #107571 (Raúl Marín).
• Switch the distroless server and keeper images to gcr.io/distroless/base-nossl-debian13 so they only ship the libraries ClickHouse actually links against and stop pulling in ones we statically link ourselves. #107837 (Rahul Nair).
• Re-enable 50 stateless tests on macOS (arm_darwin) that were stale-skipped, and use fsync instead of F_FULLFSYNC for directory syncing on macOS. #107887 (Raúl Marín).

ClickHouse release 26.5, 2026-05-21. Presentation, Video

Backward Incompatible Change

• Changed defaults of date_time_input_format and cast_string_to_date_time_mode from basic to best_effort. Queries that previously failed to parse non-basic datetime strings (e.g. 2024 April 4, Apr 15, 2020 10:30:00) may now succeed by default. To keep the old strict parsing behavior, set these settings to basic (or use compatibility). #89334 (Alexey Milovidov).
• Tuple element name null is now forbidden because it conflicts with the subcolumn name used for Nullable null maps, causing ambiguous subcolumn resolution. #98377 (Alexey Milovidov).
• Add a setting dynamic_disk_allow_from_env, dynamic_disk_allow_from_zk, dynamic_disk_allow_include to disallow usage of from_env, from_zk, include in dynamic disks. Backward Incompatible Change because prohibits by default the behaviour which used to be allowed by default. #99138 (Kseniia Sumarokova).
• You can no longer use the obsolete Arrow-based Parquet reader and writer. The native implementation will be used instead. #100949 (Alexey Milovidov).
• SHOW CREATE TABLE t now prefers the temporary table when both a permanent and a temporary table named t exist and no database is specified, matching the existing behavior of DESCRIBE TABLE. Additionally, DESCRIBE TEMPORARY TABLE syntax is now supported. #100966 (Alexey Milovidov).
• Reduced default http_max_fields from 1,000,000 to 1,000 and http_max_field_name_size from 128 KB to 4 KB to limit pre-authentication memory usage by HTTP connections. Added http_max_request_header_size and http_headers_read_timeout settings. Users who rely on the previous higher limits can restore them via settings. #103285 (Sema Checherinda).
• Added a histograms nested column to system.metric_log that snapshots every registered histogram metric per row, with a new system_metric_log_show_zero_values_in_histograms setting to control zero-value emission. Deprecates the system.histogram_metric_log table. #103770 (Miсhael Stetsyuk).
• CAST to DateTime or DateTime64 without an explicit time zone now preserves the time zone of its source argument (when the source is a DateTime/DateTime64 with an explicit time zone), matching the behavior of the toDateTime/toDateTime64 functions. Closes #55072. #104433 (Alexey Milovidov).
• Removed the kql table function. Use SET dialect = 'kusto' to run queries in the KQL dialect. #105101 (Alexey Milovidov).
• The window functions RANK and DENSE_RANK now reject arguments and throw NUMBER_OF_ARGUMENTS_DOESNT_MATCH, in line with the SQL standard. Previously, queries such as RANK(x) OVER (ORDER BY id) were silently accepted with the argument ignored. To restore the previous lenient behavior, set allow_rank_dense_rank_arguments = 1. Closes #49526. #104324 (Groene AI).

New Feature

• Added a new setting max_bytes_ratio_before_external_join, mirroring max_bytes_ratio_before_external_group_by and max_bytes_ratio_before_external_sort. It expresses the spill-to-disk threshold for hash joins as a fraction of available memory; combined with the absolute max_bytes_before_external_join, the smaller resulting threshold applies. #103862 (Alexey Milovidov). The new max_bytes_ratio_before_external_join setting is now enabled by default at 0.5, mirroring max_bytes_ratio_before_external_group_by and max_bytes_ratio_before_external_sort. Hash joins automatically spill to grace hash join once the right-side data exceeds half of the available system memory (when memory limits are configured). #104285 (Alexey Milovidov).
• Add table function filesystem. It allows to represent directory structure as a table, to query files' metadata and contents with SQL. Originally #42039 by @perst20. See #42039. See #50208. #53610 (Alexey Milovidov).
• Allow passing bare function names to higher-order functions like arrayMap, arrayFilter, etc. For example, arrayMap(negate, [1, 2, 3]) is now equivalent to arrayMap(x -> negate(x), [1, 2, 3]). #101033 (Alexey Milovidov).
• Add setting send_table_structure_on_insert_with_inline_data and --inline-insert-data client option to allow the server to parse inline INSERT data itself over the native protocol, avoiding the round-trip to receive table structure and improving performance for many small inserts. #101034 (Alexey Milovidov).
• Add tokenizeQuery and highlightQuery functions for SQL query tokenization and syntax highlighting. tokenizeQuery returns lexer tokens with byte offsets and token types; highlightQuery returns parser-based syntax highlighting ranges with highlight categories (keyword, identifier, function, number, string, etc.). #101054 (Alexey Milovidov).
• Add url_base setting to resolve relative URLs in the url table function and URL table engine, following RFC 3986 semantics. #101113 (Alexey Milovidov).
• Support negative values in the LIMIT BY clause to select rows from the end of each group instead of the beginning. For example, LIMIT -2 BY id returns the last two rows per id. Negative offsets (LIMIT -1 OFFSET -1 BY id) and mixed signs (LIMIT -2 OFFSET 1 BY id) are supported as well. #103222 (Nihal Z. Miaji).
• Support json_value function to output with tuple and array to improve performance of multiple json query. #78362 (kevinyhzou). Support multi-path Tuple/Array JSONPath argument in JSON_VALUE, JSON_EXISTS, and JSON_QUERY, by @KevinyhZou. #101102 (Alexey Milovidov).
• A new kafka_autodetect_client_rack parameter is introduced. If set, discover the Availability Zone via cloud facilities and propagate it as the client.rack parameter of librdkafka to avoid cross-zone communications. #81323 (Ilya Golshtein).
• Add Read event type to system.blob_storage_log for tracking object storage read operations, controlled by new setting enable_blob_storage_log_for_read_operations. #96867 (Alexey Milovidov).
• Users can now see ZooKeeper watches issued by clickhouse-server using the new system.zookeeper_watches table. #99277 (Den Kalantaevskii).
• Added Shards profile event that counts the number of shards involved in distributed queries, summed across all tables. #99470 (Alexey Milovidov).
• WASM UDFs can be declared DETERMINISTIC and become a subject of constant folding. #100005 (Vasily Chekalkin).
• Add parallel_replicas_prefer_local_replica setting: when disabled, parallel replicas are selected purely by the load balancing algorithm, allowing even max_parallel_replicas = 1 queries to be directed to another host. #100139 (Alexey Milovidov).
• Add {disk,storage,http}_connections_rcvbuf and {disk,storage,http}_connections_sndbuf server settings to control TCP socket buffer sizes on outgoing HTTP connections, allowing operators to override kernel autotuning and cap per-connection memory usage. #100478 (Sema Checherinda).
• Support CREATE OR REPLACE MATERIALIZED VIEW with the same atomic swap semantics as CREATE OR REPLACE TABLE. Works with inner tables, TO tables, POPULATE, REFRESH, and ON CLUSTER. #100539 (DQ).
• Add s3_read_request_duration_microseconds and s3_read_request_bytes histogram metrics to observe S3 GET request connection lifetime and bytes consumed, visible in system.histogram_metrics and the Prometheus endpoint. #102058 (Sema Checherinda).
• Add Paimon, PaimonS3, PaimonAzure, PaimonHDFS, and PaimonLocal table engines with incremental read support backed by Keeper snapshot progress tracking. Incremental mode returns only new rows since the last committed snapshot. Targeted snapshot delta reads are available via paimon_target_snapshot_id, and per-query snapshot caps via max_consume_snapshots. Background metadata refresh is configurable with paimon_metadata_refresh_interval_sec. Gated by allow_experimental_paimon_storage_engine. #102343 (XiaoBinMu).
• Added a new Kafka table setting kafka_map_virtual_columns_on_write. When enabled, columns named _key, _timestamp, _headers.name and _headers.value in the Kafka table schema are produced as the corresponding Kafka message key, timestamp and headers on INSERT, and are excluded from the message payload. #103243 (Alexey Milovidov).
• Added SYSTEM PAUSE VIEW [db.]name and SYSTEM PAUSE VIEWS queries for refreshable materialized views. Unlike SYSTEM STOP VIEW, SYSTEM PAUSE VIEW does not interrupt the currently running refresh — the in-flight refresh is allowed to complete and only subsequent refreshes are prevented. Undone by SYSTEM START VIEW or SYSTEM START VIEWS, which now uniformly clear both the stopped and paused states. #103252 (Nikita Mikhaylov).
• Added function regexpPosition (with PostgreSQL-compatible aliases regexpInstr and regexp_instr) that returns the byte position of the N-th regex match in a string. Supports start offset, return-after-match mode, regex flags, and capture-group selection. #104172 (Abhinav Agarwal).
• New functions isPrime and isProbablePrime for primality checks. isPrime returns an exact result for unsigned integers up to UInt64. isProbablePrime also supports UInt128 and UInt256; for those wider types, 0 means definitely composite and 1 means probably prime. The optional second argument of isProbablePrime, rounds, controls the confidence (capped at 256); the default of 25 rounds bounds the false-positive rate for a random composite below 10^-15, and isProbablePrime is cancellable. #104234 (Nihal Z. Miaji). #104639 (Alexey Milovidov). #104806 (Nihal Z. Miaji).
• clear and /clear now clear the terminal in the clickhouse command-line tools instead of running as a mistaken query. #104318 (Tyler Hannan).
• Allow the file table function to accept an Array(String) of paths in SELECT queries. #104442 (Yue).
• Add deterministic and higher_order columns to system.functions table. #104479 (Pedro Ferreira).
• Add an optional encoding variant parameter to bech32Encode (bech32 / bech32m) and a raw decode mode to bech32Decode for non-SegWit address encoding (e.g. Cosmos SDK, Injective, Osmosis). #98986 (Yash ).
• You can now write data in AvroConfluent format, which was previously input-only. This enables producing Confluent Schema Registry-framed Avro messages directly from ClickHouse, for example when writing to Kafka. The schema is automatically registered with the registry. Use the new output_format_avro_confluent_subject setting to specify the subject name. #101935 (János Benjamin Antal).
• Added the prettyPrintJSON function to format a JSON string into a human-readable form. Useful for dashboards or reports where prettifying previously required an extra step on the client side. Closes #62523. #102594 (Dmitry Prokofyev).
• Added STRING_AGG as a case-insensitive alias of groupConcat for PostgreSQL / SQL-standard compatibility. #105125 (Alexey Milovidov).
• Individual subquery results can now be cached independently using SETTINGS use_query_cache = true on specific subqueries, without caching the entire outer query. A new setting query_cache_for_subqueries = true enables bulk propagation of use_query_cache into all subqueries. Note: use_query_cache on the outer query no longer auto-propagates to subqueries. #99804 (Vincent Voyer).
• Added lexer-based syntax highlighting to the query editor in the Web UI (play.html), modelled after clickhouse-client colors. #105105 (Alexey Milovidov).

Experimental Feature

• Added an experimental web terminal interface at /webterminal that provides an interactive clickhouse-client session in the browser over WebSocket. Disabled by default; enable with the allow_experimental_webterminal server setting. See it here. #100277 (Alexey Milovidov). #105191 (Alexey Milovidov). #105059 (Alexey Milovidov).
• The Kafka2 engine (experimental, with Keeper-based offset storage) now supports direct SELECT queries and the kafka_commit_on_select setting. #100276 (Alexey Milovidov).
• WASM UDFs can now coerce more numeric types: smaller integers to wider integers (e.g. Int8 to UInt64), and any integer to floating point (e.g. Int32 to Float32). #100435 (Vasily Chekalkin).
• Support LIKE function in DELETE FROM system.webassembly_modules query. #104397 (Vladimir Cherkasov).
• Support geo types for Iceberg. #103113 (Konstantin Vedernikov).
• Add prepared statements functionality to ArrowFlight SQL server. #103047 (Yakov Olkhovskiy).
• Improved KQL parser (for the Kusto language support) robustness by preserving parser depth and backtracks counters across KQL parser stages, so parser limits are tracked consistently for complex KQL queries. #103528 (Yakov Olkhovskiy).

Performance Improvement

• Reuse the Parquet footer metadata cache when reading local Parquet files via the file table function or File table engine. Previously the cache was only consulted for object-storage backends. #104260 (Alexey Milovidov).
• Push ORDER BY ... LIMIT n through LEFT/RIGHT joins when the sort key only references columns from the side preserved by the join, restricting how many rows the preserved-side input must produce before joining. Controlled by the new setting query_plan_top_k_through_join (default enabled). #104268 (Alexey Milovidov).
• Enable use_top_k_dynamic_filtering and use_skip_indexes_for_top_k settings by default to improve performance of ORDER BY ... LIMIT N queries. #99537 (Alexey Milovidov). Restrict use_top_k_dynamic_filtering to fixed-length sort columns by default, avoiding regressions on ORDER BY <var-length-column> LIMIT N queries where the per-row threshold comparison cost exceeds the I/O savings. The previous behavior is available via the new use_top_k_dynamic_filtering_for_variable_length_types setting. #104216 (Alexey Milovidov).
• Use the oversize-arena feature of jemalloc to reduce page faults. #103958 (Nikita Taranov).
• Limit simultaneously active streams in UNION ALL to reduce peak memory usage. #100176 (Alexey Milovidov).
• Slightly optimize the userspace page cache. #100300 (Alexey Milovidov). Now the userspace page cache is always better than the OS page cache.
• Cold reads of object storage through the userspace page cache (use_page_cache_for_object_storage = 1) are now significantly faster, because consecutive cache misses are coalesced into a single HTTP request instead of one request per page_cache_block_size block. #104230 (Alexey Milovidov).
• Speed up the index analysis involving type casting and function application. Closes #55653. #100366 (Alexey Milovidov).
• Speed up huge queries on Merge tables over a huge number of underlying tables. Closes #32465. #100369 (Alexey Milovidov).
• Remove vtable from setting field types, reducing Settings copy size by ~28x and improving cache locality via typed-array layout for all settings types. #102269 (Raúl Marín).
• Add max_threads_min_free_memory_per_thread and max_insert_threads_min_free_memory_per_thread settings to automatically reduce query parallelism when the server is low on free memory. #100383 (Alexey Milovidov).
• Reduce memory usage on low-memory systems (< 4 GiB). #100389 (Alexey Milovidov).
• Added OptimizeTrivialGroupByLimitPass. For trivial SELECT ... FROM t GROUP BY k LIMIT n queries (no HAVING, ORDER BY, or window functions), the analyzer now sets max_rows_to_group_by = n + offset with group_by_overflow_mode = 'any', so aggregation stops once n distinct keys have been produced instead of grouping the entire input. Controlled by the new setting optimize_trivial_group_by_limit_query (enabled by default). #104473 (Amos Bird) (Alexey Milovidov).
• Granule-level implicit min-max index for the _part_offset and _block_number virtual columns, including for projections. Enables fast pruning of granules based on virtual column predicates. #103952 (Mikhail Artemenko). #104746 (Mikhail Artemenko). #105137 (Mikhail Artemenko).
• For the prealloc_serialized family of aggregation methods, precompute per-row hashes during the batch-serialization pass and use them to (a) skip rehashing in emplaceKey/findKey and (b) software-prefetch the next row's bucket. Speeds up multi-key string/serialized aggregation by hiding hash-table cache-miss latency. #104475 (Amos Bird) (Alexey Milovidov).
• Query condition cache for Iceberg tables. #102115 (Konstantin Vedernikov).
• Optimize cramersV, cramersVBiasCorrected, theilsU, and contingency when used with window functions. Closes #83521. #93384 (Nihal Z. Miaji).
• Added a query optimization that rewrites tupleElement(dictGet('dict', ('a', 'b', 'c'), key), N) into dictGet('dict', 'a', key), avoiding fetching unnecessary dictionary attributes. Controlled by the optimize_dictget_tuple_element setting (enabled by default). #100186 (Alexey Milovidov).
• Enable buffering for sorting steps on the initiator for distributed queries with sorting. #100661 (Nikita Taranov).
• Performance improvement for partial_merge JOIN. #100945 (Artem Zuikov).
• Slightly reduced memory over-allocation in partial_merge JOIN. #100963 (Artem Zuikov).
• Optimize allocations/deallocations by caching sampling settings instead of traversing the entire memory-tracker hierarchy. #101267 (Azat Khuzhin).
• Reduce memory allocation overhead during S3 multipart uploads by preallocating internal tracking containers. #101799 (Gagan Dhakrey).
• Add software prefetch in hash join probe phase to reduce memory access latency for large hash tables, controlled by setting enable_software_prefetch_in_join. #102444 (Xiaozhe Yu).
• Optimize MemoryTracker layout, improving its performance by ~25%. #103464 (Azat Khuzhin).
• Rewrite coalesce(a, b, ...) <op> const and ifNull(a, b) <op> const predicates before index analysis so per-column primary key and skip indexes on each argument can prune granules. Controlled by the new setting allow_key_condition_coalesce_rewrite (on by default). #103468 (Manuel).
• Significantly improved query performance when reading Iceberg catalogs with large JSON metadata files by optimizing escaped slash processing. #103998 (Mohaidoss).
• Avoid index uncompressed cache overhead when the cache is disabled (server setting index_uncompressed_cache_size = 0, which is the default). #104063 (Michael Kolupaev).
• Fix ORDER BY ... LIMIT queries with small limit reading excessive granules when combined with a non-selective WHERE filter. Previously, any filter above an in-order read disabled the per-mark-range task split, so the pipeline could not cancel between granules and read the whole part for each stream. #104112 (Vladimir Cherkasov).
• Fixed missing hash table sizes cache reuse after reordering JOIN sides. #104131 (Nikita Taranov).
• When fsync_after_insert is enabled, fsync of part files is now performed in parallel using the IO thread pool, speeding up insert finalization on wide tables. The full ClickBench hits load is about 22% faster. #104137 (Alexey Milovidov).
• Vectorise find_first_symbols, find_first_not_symbols, find_last_symbols_or_null, find_last_not_symbols_or_null, and splitInto on AArch64 using NEON. Previously these helpers had a SIMD path only on x86 (SSE2 / SSE4.2) and fell through to a scalar loop on ARM. Speeds up TSV parsing by ~2x, URL functions and splitByChar by ~1.3x on the ClickBench hits dataset; very dense JSON parsing (sub-16-byte field cadence) regresses slightly in line with the existing SSE2 trade-off. #104228 (Alexey Milovidov).
• Reading data through a trivial ALIAS column (e.g. some_alias['key'] where some_alias ALIAS m) now goes through the same per-subcolumn read path as referencing the underlying column directly, restoring large I/O savings for Map, Array, Tuple and Nullable aliased columns. #104245 (Raúl Marín).
• Reduced lock contention on the asynchronous remote-FS read path by making the per-query AsyncReadCounters lockless. #104374 (Nikita Mikhaylov).
• Slightly better query plan for projections in-order scan. #103723 (Mikhail Artemenko).
• Extend optimizeUseNormalProjections to also handle a specific case where nothing was filtered but the projection's sorting key can remove the sorting step from the query plan. #104680 (Mikhail Artemenko).
• Allow json.path[] syntax sugar and explicit type hints to work correctly on typed JSON paths. #99179 (Pavel Kruglov).
• Optimize json.path[N].nested.path (which expands to tupleElement(tupleElement(json.path[N], 'nested'), 'path')) into json.path[].nested.path[N], which reads much less data. #99802 (Pavel Kruglov).
• Optimize SHOW TABLES access checks in system.parts by hoisting database-level grant checks out of the per-table loop. #100860 (Shaohua Wang).
• Remove a redundant per-table SHOW TABLES access check in the SELECT name / SELECT database, name fast path of system.tables. #100881 (Shaohua Wang).
• Enable JIT compilation on macOS. #100947 (Alexey Milovidov).
• Skip deferring the row policy after FINAL when it depends only on sorting-key columns and is deterministic, and skip the corresponding PREWHERE deferral that the row policy was forcing in that case. #102884 (Yarik Briukhovetskyi).
• Added support for hasAny and hasAll as filter predicates in text indexes. #103266 (Anton Popov).
• Route long-lived MergeTree heap state (per-part and per-table metadata) to a dedicated jemalloc arena, exposed via jemalloc.mergetree_arena.* async metrics. Reduces default-arena fragmentation in steady-state and keeps per-part survivors from pinning otherwise-decayable pages. #104136 (Raúl Marín).
• Improve ZooKeeper client timeout handling under heavy load when many requests are pipelined on a single session. The ZooKeeper client now uses a progress-based timeout: as long as any data is received from the server within session_timeout_ms, the wait is extended. A hard cap of 3 * session_timeout_ms per request still bounds caller latency. Closes #100466. #104351 (Antonio Andelic).
• Move per-event trace flags into a separate array and allocate them lazily, reducing the overhead of ProfileEvents tracing. #105030 (Azat Khuzhin).
• Add compareTrackAt for ColumnDecimal, improving comparison performance for Decimal columns. #105110 (Artem Zuikov).
• Added a SIMD implementation of MD5 (AVX2 / AVX512) that hashes multiple inputs in parallel, improving throughput. #105161 (Joanna Hulboj).

Improvement

• Improve the help output for all ClickHouse applications: --help now consistently returns exit code 0, prints to stdout, and a top-level clickhouse --help lists all subcommands. Adds a --no-sudo option for clickhouse start / restart (useful in Docker), and a clickhouse help subcommand. Continuation of #58244 from @qoega. #98148 (Alexey Milovidov).
• The default of input_format_column_name_matching_mode is changed from match_case to auto. Input formats that match input column names against the table schema (JSONEachRow, CSVWithNames, JSONColumns, BSONEachRow, RowBinaryWithNames, etc.) now first try a case-sensitive match and fall back to case-insensitive matching when the case-sensitive match misses. The previous strict behavior is preserved under compatibility. #104320 (Alexey Milovidov).
• Added STDDEV as a case-insensitive alias of stddevSamp for PostgreSQL/SQL-standard compatibility. #105120 (Alexey Milovidov).
• Added array_to_string as a case-insensitive alias of arrayStringConcat for PostgreSQL compatibility. #105121 (Alexey Milovidov).
• Added unnest as a case-insensitive alias of arrayJoin for PostgreSQL compatibility (function-call form). #105124 (Alexey Milovidov).
• The progress bar in clickhouse-client now shows temporary data on disk usage (e.g. for external sort, aggregation, or JOIN) next to RAM, including a per-host breakdown for distributed queries. #105190 (Alexey Milovidov).
• Added system.predicate_statistics_log, a new sampled log of predicate filter selectivity and MergeTree index-granule pruning per query. Disabled by default; enable via the predicate_statistics_sample_rate server setting. Needed for automatic index and projection recommendations. #98727 (Yarik Briukhovetskyi).
• Allow skipping local shard with missing table when skip_unavailable_shards is enabled. #100141 (Alexey Milovidov).
• Add startup warnings (visible in system.warnings) when a Linux mdraid array is being resynchronized or is in a degraded state, as both can affect disk I/O performance or indicate disk failures. #100941 (Alexey Milovidov).
• WASM UDFs now appear in system.functions with correct origin (WasmUserDefined), syntax, arguments, and returned_value columns populated from their ClickHouse type metadata. Previously they were either missing or listed with the wrong origin as duplicates. #101053 (Vasily Chekalkin).
• The generate_series table function now supports negative step values for generating descending sequences, e.g. SELECT * FROM generate_series(99, 0, -1). #101056 (Alexey Milovidov).
• Fix Context has expired exceptions raised by some functions (dotProduct, formatRow, structureToCapnProtoSchema/structureToProtobufSchema, user-defined functions) when used in deferred execution paths such as DEFAULT/MATERIALIZED expressions and table engine settings, by ensuring those functions hold a strong context where required. #101109 (Alexey Milovidov).
• Fix spurious Cache limits violated logical errors on priorities created with zero limits (such as the per-query filesystem cache priority used when enable_filesystem_query_cache_limit is on). #101428 (Alexey Milovidov).
• Auto-detect the region for s3express endpoints. #101520 (Pradeep Chhetri).
• Support field ids for data files in Iceberg writes. Closes #102322. #102362 (Konstantin Vedernikov).
• The left panel in the web UI (play.html) now scrolls independently, stays visible when the page is scrolled, and clicking a table scrolls to the query area. #102498 (Alexey Milovidov).
• Allow opening the Play UI in a new tab via Ctrl/Cmd/Shift+click or middle-click on the ClickHouse logo in the left panel. #102501 (Alexey Milovidov).
• New metrics to track memory used by projection primary keys and projection index granularity across all tables. #102587 (Narasimha Pakeer).
• Apply max_network_bandwidth_for_user and max_network_bandwidth_for_all_users to remote filesystem reads/writes. #103080 (Azat Khuzhin).
• Improve the resilience of backups when Refreshable Materialized Views are constantly refreshed by making decisions based on the snapshotted tables' state rather than a global one. #103384 (Nikita Mikhaylov).
• SELECT * FROM system.databases now always lists data lake catalog databases regardless of the show_data_lake_catalogs_in_system_tables setting. Previously they were hidden by default, which was inconsistent with SHOW DATABASES that always showed them. #103444 (Alsu Giliazova).
• Align the default of the server setting concurrent_threads_soft_limit_ratio_to_cores in code with the shipped config.xml value (2), so the default max_min_fair concurrent threads scheduler caps query processing threads at 2x cores out of the box even when the shipped config.xml is not used. #103446 (Alexey Milovidov).
• Improved sanitizer robustness in parser and string-function edge cases by handling empty input in getURLScheme, avoiding null-pointer arithmetic in Lexer::nextToken max_query_size checks, and short-circuiting UTF-8 subsequence evaluation on empty haystacks before decoding. #103489 (Yakov Olkhovskiy).
• Improved correctness of monotonicity inference for divide(0, x) and intDiv(0, x): previously the functions were unconditionally reported as monotonic, but 0 / x is non-monotonic on any range that includes 0 because 0 / 0 is undefined (NaN/Inf for divide, division-by-zero exception for intDiv). The false claim caused KeyCondition::applyMonotonicFunctionsChainToRange to produce ranges with left > right, which tripped a LOGICAL_ERROR Invalid binary search result in MergeTreeSetIndex in debug builds when an IN / NOT IN expression on the primary key wrapped the key in divide(0, key) or intDiv(0, key). Release builds were unaffected — the assertion is gated by #ifndef NDEBUG. #103621 (Groene AI).
• Replace the HTTPConnectionPool*TCP{Rcv,Snd}BufBytes_{p50,p75,p90,p95} async metrics with a bucket-based histogram http_pool_tcp_buf_bytes (labels group, direction) in system.histogram_metrics. Per-group total async metrics are preserved. #103704 (Sema Checherinda).
• The server settings {disk,storage,http}_connections_{rcvbuf,sndbuf} are now reported as changeable without restart in system.server_settings. Their values can be updated via SYSTEM RELOAD CONFIG; the runtime application path was already in place since #100478. #103772 (Sema Checherinda).
• Add support for resolved symbols (Array(String)) in flameGraph. #103816 (Azat Khuzhin).
• CLI client can now specify <rainbow_parentheses>false</rainbow_parentheses> in its config in environments where terminal colors clash with the parentheses (similarly, clickhouse format now has --no_rainbow_parentheses). #103851 (Larry Snizek).
• Fix MultiVolnitsky UTF-8 case-insensitive search by rolling back partial putNGram inserts on failure and switching failed needles to fallback searchers, avoiding inconsistent state. #103864 (Yakov Olkhovskiy).
• Implement sched_getcpu via rseq TLS in glibc-compatibility musl. #104016 (Azat Khuzhin).
• Replicated refreshable materialized view in APPEND mode will no longer refresh twice if connection to zookeeper was briefly lost during refresh. #104051 (Michael Kolupaev).
• Allow Distributed tables without an explicit column list to validate sharding keys against the inferred remote table structure. #104111 (Yue).
• Fix REST catalog with Azure abfss path. #104120 (Konstantin Vedernikov).
• Honor role_arn and role_session_name auth settings in the Keeper S3 snapshot client, allowing snapshot uploads to use STS AssumeRole-based authentication. #104140 (Alexey Milovidov).
• Fix a memory leak when running queries with MATERIALIZED CTEs. #104153 (Alexey Milovidov).
• Fix lowerUTF8 / upperUTF8 exception when processing large non-ASCII data sets (e.g. during text-index builds) where the accumulated output buffer would exceed 2 GiB; reject excessively long single rows with a clear error. #104229 (Shaohua Wang).
• Harden MergeTree column-statistics loading against transient I/O failures to prevent permanently disabling statistics-based optimizations for affected parts. #104372 (zoomxi).
• INSERT INTO ... SELECT FROM input(...) no longer requires the CREATE TEMPORARY TABLE grant. #104470 (Alexey Milovidov).
• Added a new MergeTree setting concurrent_part_removal_threshold_for_remote_disk (default 16) that is used instead of concurrent_part_removal_threshold when at least one part being removed is stored on a remote disk. The previous threshold of 100 could make DROP TABLE and other part-removal operations on object storage backends stall for tens of seconds because removals were performed serially even though each one is a separate network round-trip. The new setting causes the parallel removal path to be entered much sooner on remote storage, while leaving local-disk behavior unchanged. #104676 (Groene AI).
• New setting defer_partition_pruning_after_final (default 1) makes the 26.3-introduced behavior of skipping partition pruning under FINAL opt-out. Set it to 0 to restore pre-26.3 partition pruning — substantially faster on event-log workloads where same-PK rows cannot span partitions. compatibility = '26.2' flips it to 0 automatically. #104705 (Nikita Fomichev).
• Fix intExp2 returning wrong results for out-of-range inputs (shifts >= 64 under JIT, and integers with magnitude exceeding INT_MAX on both code paths). #105054 (Raúl Marín).
• Quote shell arguments built from CLI options and parsed input in clickhouse install and clickhouse git-import so paths, user/group names, and commit hashes containing whitespace or shell metacharacters are handled correctly. #105232 (Raúl Marín).
• The Alias table engine is now non-experimental and available without the allow_experimental_alias_table_engine setting. #103488 (Alexey Milovidov).
• Added --queries-format option to clickhouse-benchmark to choose between the default tab-escaped one-query-per-line input (tsv) and parsing standard input as a script of multiple queries separated by ; (script). #99972 (Aleksandr Musorin).
• The element-wise tuple operators tuplePlus, tupleMinus, tupleMultiply, tupleDivide, tupleModulo, tupleIntDiv, and tupleIntDivOrZero are now variadic and accept two or more tuples of the same size, applied element-wise as a left-fold. They previously accepted exactly two arguments only. #104659 (Aruj Bansal).
• Added a new built-in web UI at /processors-profile that visualizes the pipeline of any past SELECT query as a heatmap, sourced from system.query_log and system.processors_profile_log. Each processor is colored by its elapsed_us and shows per-processor stats (rows, bytes, wait times) on hover. #104614 (Nikita Mikhaylov).
• Setting query_plan_use_logical_join_step (and its alias query_plan_use_new_logical_join_step) is now obsolete and has no effect; the logical join step is always used. #104017 (Vladimir Cherkasov).
• The user input on play.html and the other built-in web pages (dashboard.html, jemalloc.html, merges.html, binary.html, webterminal.html) is no longer pre-filled with the literal text default. It now shows a user placeholder hint and is empty by default. When left empty, the page does not send a user= URL parameter (and the WebTerminal auth JSON omits the user field), so the server applies its usual fallback to the default user — and HTTP credentials supplied via other channels (X-ClickHouse-User, HTTP Basic, per-handler <handler><user> configuration) are no longer overridden. #105254 (Alexey Milovidov).
• ORC reader: decouple offset-based read (readBigAt) from use_prefetch, so EC-encoded data on HDFS can be read correctly even when use_prefetch = false (e.g. by Gluten). #103348 (zhanglistar).
• Files downloaded from play.html with the CSVWithNames format now use the .csv file extension. #103737 (JackFielding).
• More input validation for the BigLake catalog. #105117 (Konstantin Vedernikov).

Bug Fix (user-visible misbehavior in an official stable release)

• Fix inconsistent formatting by remembering if an expression was parenthesized. #92340 (Alexey Milovidov).
• Fix accurate comparison between Decimal and Float types. #94293 (zoomxi).
• Allow positional arguments in distributed queries. #94359 (simonmichal).
• Fix assertion failure in DatabaseCatalog::updateDependencies when dropping and recreating a materialized view with the same name; also fix view dependencies being silently lost during RENAME TABLE or EXCHANGE TABLES when referential dependencies were empty. #98779 (Alexey Milovidov).
• Fixed a server abort (assertion failure in DatabaseCatalog::getTableImpl) that occurred when creating a table via ON CLUSTER with a UUID identical to an existing database's UUID. #98861 (xiaohuanlin).
• Fixed usage of skip indexes on data read (with enabled setting use_skip_indexes_on_data_read) and existing patch parts created by lightweight updates. #99543 (Alexey Milovidov).
• Fix "Not-ready Set" exception when a filter with IN (subquery) is moved to PREWHERE by the query optimizer. #100375 (Alexey Milovidov).
• Fix "Cannot find column" error when combining ADD COLUMN with RENAME COLUMN in a single ALTER TABLE statement. #100387 (Alexey Milovidov).
• Fix views with mixed UNION and INTERSECT/EXCEPT operators returning wrong results after DETACH/ATTACH or server restart. #100390 (Alexey Milovidov).
• Fix "Trying to execute PLACEHOLDER action" exception that could occur during stress testing with the AST fuzzer when a correlated subquery appeared in an IN clause. #100398 (Alexey Milovidov).
• Fix logical error exception when inserting into an Iceberg table with a Date column partitioned by year, month, or day transforms. #100404 (Alexey Milovidov).
• Fix skip index being used with incompatible data after ALTER TABLE MODIFY COLUMN changes the column type, which could cause server crashes in sanitizer builds or incorrect query results. #100526 (Alexey Milovidov).
• Fix credential leak in query_log for paimonCluster, paimonS3Cluster, paimonAzureCluster, and deltaLakeS3 table functions. #100529 (JIaQi Tang).
• Fix DROP TABLE on Kafka engine tables potentially hanging indefinitely due to a deadlock in rd_kafka_consumer_close. #100604 (Alexey Milovidov).
• Replace the hardcoded source_table_engines list with runtime lookup via StorageFactory and DatabaseFactory. Add source_access_type to DatabaseFactory::EngineFeatures so that CREATE DATABASE with source engines (PostgreSQL, MySQL, S3, etc.) requires the same source grants as CREATE TABLE. Fixes GRANT TABLE ENGINE ON * failing with table_engines_require_grant=false. Closes #71544. #100746 (pufit).
• Fix server crash when reading from a table whose ALIAS column contained a correlated subquery nested inside a function call (e.g. ALIAS toString(intDivOrZero(x, (SELECT ...)))). CREATE TABLE and ALTER TABLE now reject any subquery at any depth in DEFAULT / ALIAS / MATERIALIZED column expressions with THERE_IS_NO_DEFAULT_VALUE. Previously, the shallow validation accepted nested subqueries, so the correlated case crashed at read time and the nested non-correlated case appeared to work but could lead to unexpected behavior; both are now rejected at DDL time. #100753 (Groene AI).
• Fixed a server crash (Logical error: Bad cast from type DB::FunctionNode to DB::ColumnNode) that could occur when using queries with correlated subqueries on tables that have CONSTRAINT ... ASSUME definitions, when optimize_substitute_columns and convert_query_to_cnf settings are enabled. #100756 (Groene AI).
• Fix an exception that could occur when inserting a row into a JSON column where the row introduced a new dynamic field alongside a typed field with an incompatible value, and the column was subsequently used as a GROUP BY key. #100758 (Jimmy Aguilar Mena).
• Fix workload IO scheduling being silently bypassed for S3/object-storage writes that go through the DiskObjectStorageTransaction path (used by s3_with_keeper disks and explicitly when use_fake_transaction=false). Previously, INSERT writes into MergeTree tables on such disks ignored CREATE RESOURCE / CREATE WORKLOAD throttling because the resource link was never injected into WriteSettings for the transactional write path. #100777 (JIaQi Tang).
• Fix shared schema-cache collision between Protobuf and ProtobufList: reading a message first as FORMAT Protobuf and then as FORMAT ProtobufList could fail because ProtobufList forced the cached schema into its envelope form. ProtobufList now falls back to the cached message type when no envelope schema is available. #100849 (Callum Cooper).
• Fix heap-buffer-overflow in Rust CXX bridge due to std::exception ABI mismatch. #100931 (Azat Khuzhin).
• FunctionVariantAdaptor now throws ILLEGAL_TYPE_OF_ARGUMENT when all Variant alternatives are incompatible with a function, instead of silently returning Nullable(Nothing). Previously, a WHERE function(variant_col) predicate where no alternative type was compatible would return 0 rows with no error, while the equivalent SELECT context already threw correctly. #100939 (Vasily Chekalkin).
• TRUNCATE ALL TABLES no longer fails when the database contains views. #100943 (Alexey Milovidov).
• Fix the optimize_rewrite_array_exists_to_has optimization to correctly handle type-incompatible cases (e.g. Date vs String) and re-enable it by default. #100944 (Alexey Milovidov).
• Fix S3 settings priority so that storage_configuration disk settings override global <s3> section, and user/profile/query-level settings override both. #100975 (Alexey Milovidov).
• Fix sparse serialization losing the sign of negative zero (-0.0) for BFloat16, Float32, and Float64 columns. #100983 (Takumi Hara).
• Fixed two bugs in the WKT geometry parser used when reading WKT-encoded GeoParquet and Arrow files: MULTILINESTRING geometries were incorrectly parsed as Polygon (causing an exception for typed columns and silent data corruption for mixed Geometry columns), and a malformed WKT string with no type keyword triggered undefined behaviour instead of a clean error. #100997 (Vasily Chekalkin).
• Fix grouping/GROUPING SETS queries on Distributed tables with a single shard that failed with "Method executeImpl is not supported for 'grouping' function". #101030 (Alexey Milovidov).
• Fix LOGICAL_ERROR "Column identifier is already registered" in the planner that could occur when the same table expression was processed multiple times. #101048 (Alexey Milovidov).
• Fix LOGICAL_ERROR exception "Column identifier is already registered" when additional_result_filter setting is used with UNION or EXCEPT queries. #101051 (Alexey Milovidov).
• Fixed server crash (Logical error: Bad cast from ColumnVector to ColumnNullable) when using * APPLY with aggregate functions and group_by_use_nulls=1 with GROUPING SETS, ROLLUP, or CUBE. #101062 (Groene AI).
• Fix infinite loop when input_format_csv_skip_first_lines or input_format_tsv_skip_first_lines exceeds the number of lines in the file. #101111 (Alexey Milovidov).
• Fix out-of-bounds access in lazy materialization optimization that could cause an exception in debug builds. #101144 (Alexey Milovidov).
• Fix type inference in recursive CTEs: column types are now iteratively widened via getLeastSupertype across the non-recursive and recursive sides of the UNION ALL until convergence, preventing integer overflow in expressions like x + 1. #101155 (Alexey Milovidov).
• Clamp MergeTree compress block size settings (max_compress_block_size, min_compress_block_size, marks_compress_block_size, primary_key_compress_block_size) to 256 MiB to prevent server crash when extreme values are set via CREATE TABLE SETTINGS. #101159 (Groene AI).
• Fix a LOGICAL_ERROR crash in QueryAnalyzer::resolve() when a ROW POLICY uses a scalar subquery in its USING clause (e.g. USING (SELECT 1)). Closes #100695. #101263 (Groene AI).
• Fix undefined behavior in MergeTreeDataPartWriterCompact::cancel when a stream allocation fails. #101292 (Alexey Milovidov).
• Fixes a case where timezone was not included during the assignment in the ALTER statement. Closes #101328. Related https://github.com/ClickHouse/ClickHouse/pull/100647. #101403 (Yarik Briukhovetskyi).
• Fix server crash (LOGICAL_ERROR) for INSERT SELECT queries with ORDER BY ALL when the SELECT pipeline produces multiple streams. #101443 (Groene AI).
• Fix incorrect query results caused by join reordering pushing an INNER JOIN filter (referencing only the preserved side of an outer join) into the outer join’s ON clause. #101504 (Vladimir Cherkasov).
• Skip applying lazy materialization for plans with arrayJoin, which could lead to limit not being respected. Close #101608. #101644 (Vladimir Cherkasov).
• Fix incorrect JOIN query results when mergeFilterIntoJoinCondition optimization silently dropped a WHERE equality condition with mismatched types. #101652 (Xiaozhe Yu).
• Fix the error test hint not working for syntax/parsing errors — previously -- { error SYNTAX_ERROR } on a malformed query would fail with "Expected server error" instead of matching the client-side parse error. #101675 (Groene AI).
• Fix INTO OUTFILE ... TRUNCATE not actually using atomic rename — the write went directly to the original file instead of a temp file, so on query failure the original content was destroyed. Now the data is written to a temp file and renamed only on success. #101884 (Pablo Marcos).
• Fixed an exception Unsupported DeltaLake type: varchar(n) when reading Delta Lake tables whose schema contains varchar(n) or char(n) column types. These types are now mapped to String, consistent with how the Delta Lake protocol stores them as plain byte arrays in Parquet. #101973 (Flavio Malavazi).
• Fix silent data loss when reading tar archives from S3 with schema_inference_mode=union and heterogeneous Parquet schemas — the Parquet metadata cache incorrectly reused the first file's metadata for all subsequent files in the archive. #101990 (Ahaan Limaye).
• Fix server crash (LOGICAL_ERROR) when executing ALTER TABLE UPDATE/DELETE on Iceberg tables when no prior SELECT or INSERT was done on the table in the same server lifetime. #102113 (Alexey Milovidov).
• Fix possible crash when an ALTER query executed on tables from in-memory database (e.g. temporary tables). #102360 (Den Kalantaevskii).
• Fixed formatQuery producing duplicate grants like GRANT FILE ON *.*, FILE ON *.* TO x instead of GRANT FILE ON *.* TO x when formatting backward-compatible READ/WRITE grants on the same source. #102411 (Groene AI).
• Fix lost parallelism for aggregation after read-in-order queries when max_streams_to_max_threads_ratio is greater than 1. #102467 (Alexey Milovidov).
• Fixed a crash (LOGICAL_ERROR: Unknown virtual column) when selecting subcolumns (like .null for Nullable, .size0 for Array, tuple elements, or map keys/values) from a Buffer table engine. #102470 (Groene AI).
• Fix exception "Cannot fold actions for projection" in join reorder optimization when a LEFT/RIGHT JOIN with join_use_nulls is combined with other joins involving more than two tables. #102516 (Alexey Milovidov).
• Fixed silent overflow in scalar pointwise operations on numericIndexedVector (e.g. numericIndexedVectorPointwiseAdd) when the scalar is out of range. Such inputs now raise INCORRECT_DATA instead of returning corrupted values. #102546 (FriendLey).
• Fix inconsistent AST formatting for INSERT with SAMPLE and query-level OFFSET. Closes #102523. #102547 (zoomxi).
• Fix LOGICAL_ERROR exception in groupConcat when deserializing a malformed aggregate function state. #102558 (Christoph Wurm).
• Now we do not accept garbage at the end of Time64 CSV values with input_format_csv_use_default_on_bad_values=0. Closes #102490. #102596 (Yarik Briukhovetskyi).
• Fix UNKNOWN_ELEMENT_OF_ENUM exception when inserting default value to JSON column with Enum typed paths. Closes #102359. #102687 (Pavel Kruglov).
• Fix columns_substreams.txt corruption during column rename in some cases. Closes #102259. #102689 (Pavel Kruglov).
• Fix inserting into Time data type during JSON parsing. Closes #102016. #102690 (Pavel Kruglov).
• Fix hex encoding of content sample in cached schema filenames. Closes #101904. #102703 (Pavel Kruglov).
• Fixed sort order violation (crash in debug, silent data corruption in release) during SummingMergeTree merge when the ORDER BY key is a hash expression over a Float32 column containing signaling NaN values. #102791 (Groene AI).
• Make DETACH DATABASE ... SYNC and other operations that call waitDetachedTableNotInUse cancellable via KILL QUERY and responsive to server shutdown, preventing indefinite hangs when a concurrent query holds a table reference. #102804 (Antonio Andelic).
• Fixed possible incorrect result of ANY RIGHT JOIN. #102893 (Nikita Taranov).
• Fix S3 requests failing with ios_base::clear: unspecified iostream_category error instead of being retried, caused by Poco BufferedStreamBuf::flushBuffer not handling short writes from the socket layer. #102894 (Sema Checherinda).
• Fix input('auto') table function failing via HTTP interface in INSERT SELECT queries. #102902 (Miсhael Stetsyuk).
• Disable trivial LIMIT optimization with row policies/additional_table_filters (to allow parallel index analysis). #102921 (Azat Khuzhin).
• Hide secret key in HMAC SQL function. Fix #102927. #102997 (Mikhail f. Shiryaev).
• Fix MULTIPLE_EXPRESSIONS_FOR_ALIAS exception raised on distributed queries that reference the same quantile call multiple times (e.g. in SELECT, HAVING, and ORDER BY) with optimize_syntax_fuse_functions enabled. #103014 (tanner-bruce).
• Fixes a case found by CI where a not-ready set was passed when the filter depends on the left-side column. Closes #102966. #103029 (Yarik Briukhovetskyi).
• Fix castOrNull to JSON in some cases. Closes #101818. #103036 (Pavel Kruglov).
• Fix SELECT DISTINCT silently returning incomplete results when an aggregate projection matched the query and some parts of the table had no projection data (e.g. the projection was added on a table that already held data, and MATERIALIZE PROJECTION was not run). Closes #102951. #103052 (Nihal Z. Miaji).
• Fix TOO_FEW_ARGUMENTS_FOR_FUNCTION exception when a WHERE predicate such as AND(OR(A, A), A) collapses to a single top-level argument during common expression extraction in the analyzer. #103072 (Peng).
• Fix a logical error Function writeSlice expects same column types for GenericArraySlice and GenericArraySink raised when evaluating if/ifNull over tuples, maps, or arrays containing a QBit element. ColumnQBit::structureEquals incorrectly compared the inner tuple of one QBit column against the outer wrapper of the other, so structurally identical QBit columns were reported as different. #103084 (Groene AI).
• Make DETACH DATABASE with database_atomic_wait_for_drop_and_detach_synchronously respect KILL QUERY instead of hanging indefinitely when a table reference is held. #103095 (Alexey Milovidov).
• Fix segfault when deleting WASM module using non-identifier predicate (e.g. WHERE 1=1). #103101 (Joe Redfern).
• Fix backward compatibility break where old clients fail with UNEXPECTED_PACKET_FROM_SERVER when inserting into a newer server via remote() or distributed tables, caused by unconditional sendProgress at the end of processInsertQuery. #103148 (Sema Checherinda).
• IN with non-constant tuple second argument must not CAST tuple elements down to the LHS type, this can overflow. Closes #103055. #103169 (Yarik Briukhovetskyi).
• Fix use-of-uninitialized-value in protocol function. #103187 (Pavel Kruglov).
• Fix LOGICAL_ERROR (Bad cast … to ColumnLowCardinality) during MergeTree index analysis when a WHERE clause compares a LowCardinality key column with a constant cast to a type that contains nested LowCardinality (for example Variant(LowCardinality(Date), String)). #103211 (Groene AI).
• Fix Logical error: 'index < bucket_count' in the timeSeries*ToGrid aggregate function family (e.g. timeSeriesResampleToGridWithStaleness, timeSeriesChangesToGrid, timeSeriesResetsToGrid, timeSeriesRateToGrid) when called with extreme timestamp parameters that would overflow signed 64-bit arithmetic in the bucket count computation. Also cap the total number of grid buckets at 16 million to prevent accidental large-memory allocation from adversarial inputs. #103223 (Groene AI).
• Fix Logical error: 'Port is already connected' exception during pipeline expansion in the lazy FINAL path for ReplacingMergeTree. The bug affected queries with query_plan_optimize_lazy_final = 1 when ReadFromMergeTree::initializePipeline inserted internal transforms (e.g. a Resize) that wired the sub-pipeline's processors together, causing LazyUnorderedReadFromMergeTreeSource::expandPipeline to try to connect output ports that were already connected. #103230 (Groene AI).
• Fix wrong results from LIMIT BY and DISTINCT when the input is a UNION ALL of sorted subqueries. The query plan optimizer incorrectly treated such a union as globally sorted, causing extra rows to be returned. #103231 (Nihal Z. Miaji).
• Fix possible crash during statistics calculation in Map type with lazy replication. Closes #102390. #103273 (Pavel Kruglov).
• Fix a data race for ClickHouse, MySQL, PostgreSQL and XDBC dictionary sources where clone() const reads from and isModified() const writes to the same invalidate_query_response string. #103277 (Miсhael Stetsyuk).
• Fix incorrect monotonicity detection for Date32. Closes #101265. #103283 (Yarik Briukhovetskyi).
• Cap pre-auth TCP Hello packet strings to 64 KB and add handshake_timeout_milliseconds server setting to limit total handshake time, preventing unauthenticated clients from consuming excessive memory or holding threads indefinitely. #103284 (Sema Checherinda).
• Fix Parquet ColumnIndex stats min_value > max_value for String columns. #103334 (Saurabh Kumar Ojha).
• Fix incorrect handling of NULL rows for Nullable(Tuple(...)) inputs in flattenTuple and tupleToNameValuePairs. flattenTuple now preserves the outer null map so NULL rows stay NULL. tupleToNameValuePairs now changes the result's value type to Nullable(T) when possible when the input is Nullable(Tuple(...)), so NULL rows produce [('a', NULL), ('b', NULL)] instead of [('a', 0), ('b', 0)]. When the element type cannot be wrapped in Nullable (e.g. Array), default values are used instead of NULL. Closes #103312. #103383 (Nihal Z. Miaji).
• Check for malformed flattened Dynamic data in Native format. #103392 (Pavel Kruglov).
• Fix stale RPC causing replication stall after snapshot sync. #103406 (Seva Potapov).
• Fix a LOGICAL_ERROR "Cannot pop N rows from X" that aborted the server (in debug / sanitizer builds) when reading a malformed BSON document containing a value whose BSON type is incompatible with the target column type inside a Nullable(T) or Array(Nullable(T)) column. The malformed row now produces a clean ILLEGAL_COLUMN exception as intended. #103418 (Groene AI).
• Fix a server abort in arrayFill and arrayReverseFill when applied to an Array(String) column whose first row is empty together with a constant-false lambda. The aggregate / sub-array loop underflowed a size_t index to SIZE_MAX, which then caused an out-of-bounds read inside ColumnString::doInsertManyFrom. Same bug family as #12263. #103424 (Groene AI).
• Fixes ACCESS_DENIED / UNKNOWN_TABLE in downstream APPEND RMVs with SQL SECURITY DEFINER when an upstream REPLACE RMV's EXCHANGE flips the target storage identity mid-resolution. #103427 (Alexander Gololobov).
• Populate _time column from url table function. #103437 (Nikita Taranov).
• Fix potential out-of-bounds read in the ALP codec decompression path when processing malformed input with an invalid bit-width. #103457 (Raufs Dunamalijevs).
• Fix a bug where SYSTEM SYNC FILESYSTEM CACHE '<name>' ON CLUSTER ... could lose the cache name while formatting the query, causing remote nodes to sync all filesystem caches instead of only the requested cache. #103469 (Asish Kumar).
• Fix processing of URL-encoded path in deltaLakeAzure. Closes #103509. #103525 (Smita Kulkarni).
• Fix heap-use-after-free in multiplying an AggregateFunction state by an integer (e.g. quantilesExactState(...) * N). The exponentiation-by-squaring loop merged the state with itself, which is undefined when the aggregate function's merge reallocates its internal storage. Closes STID 0988-40af. #103536 (Groene AI).
• Fixed a rare LOGICAL_ERROR "Part X intersects previous part Y" raised during ReplicatedMergeTree table startup when two empty unexpected parts on disk had overlapping but non-containing block ranges. The exception aborted the table-attach thread and prevented the table from coming up. #103537 (Groene AI).
• Fix Logical error: Incorrect mark rows for part ... (debug-only assertion) that was triggered by mutations on MergeTree tables with non-adaptive index granularity (index_granularity_bytes = 0) whose last data mark was incomplete (most reliably reproduced via DETACH/ATTACH followed by a lightweight DELETE). #103538 (Groene AI).
• Fix clickhouse-local returning 0 rows silently when reading from /proc and /sys pseudo-files via the file() table function (e.g. SELECT * FROM file('/proc/cpuinfo', 'RawBLOB')). #103548 (Ashrith Bandla).
• Fixed handling of the max_string_length argument for the GenerateRandom table engine. #103550 (Alex Kuleshov).
• Fix masking nested credentials in logs. #103552 (Vitaly Baranov).
• Fix SVE detection using SVE instructions when unavailable. #103568 (Raúl Marín).
• Fix GenerateRandom storage args parsing. #103574 (Konstantin Bogdanov).
• Fix infinite loop on WITH FILL for data starting with ±inf. #103580 (Konstantin Bogdanov).
• Fix JSONExtract into a Variant type silently truncating fractional JSON numbers. Previously, JSONExtract('{"x": 3.14}', 'x', 'Variant(Int64, Float64)') returned Int64=3 and JSONExtract('{"x": 3.14}', 'x', 'Variant(String, Int64)') returned Int64=3, dropping the fractional part. The fractional value is now preserved losslessly: a Float64/Decimal member claims it when present, otherwise a String member captures the original JSON. Variant types containing only integer members (e.g. Variant(Int64, Int32)) and direct integer extraction (JSONExtract(json, 'Int64'), JSONExtractInt, etc.) are unchanged. #103620 (Groene AI).
• Fix SYSTEM INSTRUMENT REMOVE without arguments producing std::bad_optional_access (error code 1001) instead of SYNTAX_ERROR (error code 62). #103622 (Pablo Marcos).
• Fix logical error / undefined behavior in windowID and tumble window view when called with a timezone string as the 3rd argument. #103641 (Alexey Milovidov).
• S3 client logging now treats HTTP 400 responses that include a non-empty x-amz-bucket-region header (wrong SigV4 signing region) as an informational wrong-region case with a clearer log line instead of the generic error-style path. The STS web identity credentials provider is added to the S3 credentials chain only when web identity is configured, which reduces spurious warnings for deployments that do not use it. Closes #99140. #103673 (MeltonSmith).
• Fix SYSTEM SYNC REPLICA <db>.<tbl> IF EXISTS to silently succeed when the database does not exist, matching the existing behaviour for a missing table and the precedent set by DROP TABLE IF EXISTS. Previously the query threw UNKNOWN_DATABASE despite IF EXISTS. Closes #103629. #103689 (Groene AI).
• Fix logical error Arguments of 'plus' have incorrect data types thrown by FunctionBinaryArithmetic::executeImpl2 when a MergeTree table had Array(LowCardinality(...)) in its sort key and a WHERE clause used plus / minus between that column and an Array constant of a different element type. KeyCondition::getMonotonicityForRange now strips LowCardinality recursively before invoking the inner numeric dispatch. #103701 (Groene AI).
• Fix dynamic cache resize race in 26.1+. #103702 (Kseniia Sumarokova).
• Fixed an issue where text and bloom_filter skip indices on ALIAS columns whose expression contained a lambda with captured constants (e.g. arrayMap((k, v) -> concat(k, '=', v), mapKeys(m), mapValues(m))) were silently ignored. #103708 (Anton Popov).
• Fix position and positionCaseInsensitive with a start_pos close to UINT64_MAX getting stuck or causing a segmentation fault due to overflowing pointer arithmetic. #103766 (Raúl Marín).
• Fixes undefined behavior while parsing dateTime with a double fractional part. #103773 (Yarik Briukhovetskyi).
• Fixed a data-correctness regression in 26.x where JIT-compiled if and multiIf with a Decimal result type and a non-Decimal (integer or float) literal in one branch silently returned a value 10^scale too small. The slow (non-JIT) path was unaffected. Workaround on affected versions: SET compile_expressions = 0. #103809 (Groene AI).
• Fixes forwarding the tokenizer from the text index to supported functions. #103826 (Elmi Ahmadov).
• Fix wrong results from numbers, generate_series, and similar range-honoring sources when the WHERE clause uses IN or NOT IN over a tuple whose elements deduplicate to a single key column (for example, WHERE tuple(number, number) NOT IN (tuple(1, 2))). Closes #103660. #103835 (Groene AI).
• Keep the auto-spilling hash join's actual memory peak under max_bytes_before_external_join. Previously, statistics-driven preallocation, in-place hash table doubling, and unbounded GraceHashJoin in-memory buckets could each push the query past the configured cap and trip MEMORY_LIMIT_EXCEEDED. #103838 (Alexey Milovidov).
• Fix a hang in clickhouse-local shutdown when system logs (such as text_log or filesystem_cache_log) are configured. SystemLogs::flushImpl was calling BaseDaemon::instance().flushTextLogs(), which throws std::bad_cast outside clickhouse-server and left the saving threads running until pthread_cond_destroy blocked the destruction of the system log queues. #103874 (Alexey Milovidov).
• Reject MATERIALIZED CTE queries whose body resolves to different inferred column types in different references with a clear TYPE_MISMATCH error instead of crashing the server with a Bad cast LOGICAL_ERROR. This previously happened when the CTE body referenced identifiers from outer scope (for example an alias from the calling subquery's projection) that were inlined as different constants per reference. #103879 (Groene AI).
• Fix a use-of-uninitialized-value in the JOIN-conversion query plan optimizers (tryConvertAnyOuterJoinToInnerJoin, tryConvertAnyJoinToSemiOrAntiJoin) when the filter on top of an ANY OUTER JOIN contains a non-deterministic function such as rand, now, or rowNumberInAllBlocks. The optimizer no longer attempts to constant-fold such filters and leaves the JOIN unchanged, which also prevents incorrect conversions to INNER/SEMI/ANTI JOIN that could silently drop rows. #103880 (Groene AI).
• Fix a use-after-free in StorageKafka2 that could crash the server when a Keeper session is replaced while the consumer is holding ephemeral topic-partition locks. #103890 (Groene AI).
• Fixed a LOGICAL_ERROR "Primary key type mismatch" thrown when joining an EmbeddedRocksDB table via JOIN ... USING (key) against a subquery whose key column has a different type (e.g. Nullable(UInt64), Int64, Decimal) than the storage's primary key. The planner now declines DirectKeyValueJoin on type mismatch and falls back to HashJoin, which handles the type conversion. #103928 (Groene AI).
• SET max_threads = DEFAULT (and the same for max_final_threads and max_parsing_threads) no longer loses the auto state. Previously, after resetting one of these settings, system.settings would report the resolved core count (e.g. 32) instead of 'auto(32)', and the server would behave as if the value had been explicitly pinned. #103991 (Groene AI).
• Fix SIZES_OF_ARRAYS_DONT_MATCH when reading AggregateFunction(topK(N), String) columns whose persisted alpha_size was grown by a pre-25.12 deserialize+serialize cycle. #104002 (Raúl Marín).
• Fixed SQL injection vulnerability in PostgreSQL, Cassandra and XDBC dictionary sources: string keys containing single quotes were escaped with \' (backslash), which these backends treat as a literal backslash rather than an escape sequence, allowing arbitrary SQL to be injected into dictionary lookup queries. ExternalQueryBuilder now emits SQL-standard '' escaping for those backends; ClickHouse and MySQL dictionary sources continue to use backslash escaping. #104009 (Shaohua Wang).
• Fixed possible type mismatch in aggregation when a column type was altered to/from LowCardinality, and min-max projection wasn't rebuilt. #104013 (Nikita Taranov).
• Fix infinite loop of query optimizations caused by not propagating prevention of unused column removal when merging expressions. #104083 (János Benjamin Antal).
• Fix LOGICAL_ERROR in StreamingStorageRegistry::renameTable when batch-renaming streaming tables (S3Queue, Kafka, RabbitMQ) by using UUID-based identity tracking instead of name-based. #104101 (Nikita Taranov).
• Fixed wrong results when a CTE constructed with UNION ALL contained a SELECT DISTINCT branch and the outer query projected only a subset of the CTE's columns. The new analyzer's RemoveUnusedProjectionColumnsPass was incorrectly removing the un-referenced column from the inner DISTINCT projection, causing rows that should have remained distinct (same value in the projected column but different value in the dropped column) to collapse into one. #104114 (Groene AI).
• Fix several edge case correctness issues in setting optimize_inverse_dictionary_lookup where the optimization could silently drop rows or suppress exceptions. Closes #103270. Close #103085. #104133 (Nihal Z. Miaji).
• Fix write out of bounds while deserializing quantileTiming state. #104141 (Alexey Milovidov).
• Fix undefined behavior when an out-of-range Float64 value is converted to a wide integer type (UInt64, Int64, Int128, UInt128, Int256, UInt256). Previously, values equal to Float64(numeric_limits<T>::max()) (which rounds up to a value above the actual maximum) bypassed the bounds check and produced UB in the subsequent cast. This affected aggregate-function parameter parsing (topK, histogram, uniqUpTo, groupArrayInsertAt, etc.) and integer-typed settings via SET <setting> = <Float64>. Closes #103817. #104154 (Groene AI).
• Fix LOGICAL_ERROR exception "Unexpected return type from comparison. Expected UInt8. Got Const(Nullable(UInt8))" when comparing a nested Tuple(Tuple(Nullable(...))) (or deeper nesting) with a String literal. The comparison's return type is now correctly inferred as Nullable(UInt8), matching the runtime behaviour. #104171 (Groene AI).
• Fixed a server abort (UndefinedBehaviorSanitizer: reference binding to null pointer, segfault in release builds) on SELECT ... FROM <ReplacingMergeTree(version, is_deleted)> FINAL PREWHERE is_deleted = <expr> AND <other column expr> when query_plan_optimize_lazy_final = 1. The lazy-FINAL non-intersecting reading step lost the is_deleted column from its output header because prewhere consumed it as an input without re-exposing it as an output. The downstream addIsDeletedFilter step then dereferenced a null ActionsDAG::Node pointer. #104177 (Groene AI).
• When calling system.failpoints table, it would use a failpoint, thus possibly disabling it. #104237 (Pedro Ferreira).
• Fix MemorySanitizer: use-of-uninitialized-value in detectLanguage* functions when the input contains a UTF-8 character ending exactly at the buffer boundary. #104257 (Raúl Marín).
• Fix a logical error (Bad cast from type DB::CachedObjectStorage to DB::S3ObjectStorage) that aborted argument parsing of data-lake table functions and engines (icebergS3, deltaLakeS3, etc.) when called with SETTINGS disk = '...' against a disk whose underlying object storage is wrapped by a decorator such as a filesystem cache. Closes #89300. #104258 (Groene AI).
• Fix parsing of parenthesized subscript expressions on columns named values, for example (values['a']), so they are no longer interpreted as SQL-standard VALUES table expressions. #104312 (Desel72).
• Fix a server abort/LOGICAL_ERROR in the filesystem cache background eviction thread (SLRUFileCachePriority::collectEvictionInfo) that could fire when keep_free_space_size_ratio or keep_free_space_elements_ratio was high enough to trigger eviction while all cache entries had already been promoted to the SLRU protected queue (probationary empty). #104313 (Groene AI).
• Fix exceptions (NOT_FOUND_COLUMN_IN_BLOCK, LOGICAL_ERROR, AMBIGUOUS_COLUMN_NAME) when using projections with UNION ALL views, window functions, or alias-column name collisions. Regression from #88798. #104317 (Amos Bird).
• Fixes a possible underflow in parsing postgres arrays. #104322 (Grant Holly).
• Functions that return a non-Nullable type (such as Array, Tuple, or Map) now accept Nullable arguments. Affected functions include extractAll, extractAllGroups, extractAllGroupsHorizontal, extractAllGroupsVertical, extractGroups, splitByChar, splitByString, splitByRegexp, splitByWhitespace, splitByNonAlpha, and alphaTokens. NULL input rows produce the default value of the result type (e.g. an empty array) instead of raising "Nested type is not allowed inside Nullable type". #104326 (Alexey Milovidov).
• Fix iceberg stats with partitioned table. This closes #104321. #104329 (Konstantin Vedernikov).
• Fix a fatal logical error at server startup on macOS (and similar jemalloc builds) where Jemalloc::verifySetup incorrectly reported a jemalloc_enable_background_threads mismatch because optional background_thread / max_background_threads mallctls are absent; verification is skipped when those mallctls are unavailable, and getValue no longer leaves the output uninitialized on failure. Closes #102183. #104330 (SAYON DEEP).
• Fix a correctness regression where SELECT queries with max_rows_to_read_leaf and read_overflow_mode_leaf = 'throw' could incorrectly throw TOO_MANY_ROWS even when a skip index would have reduced the read below the leaf cap. The symmetric non-leaf settings (max_rows_to_read / read_overflow_mode) were already handled. #104331 (Groene AI).
• toUUID, toUUIDOrNull, toUUIDOrZero, toUUIDOrDefault, CAST to UUID and Nullable(UUID), accurateCastOrNull to UUID, and the input formats that parse a UUID from text (Avro, MsgPack, JSONExtract, ...) now reject strings that have the right length but contain non-hexadecimal characters. Previously such inputs were silently turned into a fabricated UUID by walking off the end of the hex digit lookup table; now toUUID throws CANNOT_PARSE_UUID, and the Or* variants return NULL / the zero UUID / the supplied default. #104370 (Groene AI).
• Fix Bad cast LOGICAL_ERROR in caseWithExpression (and SQL CASE expr WHEN ... THEN ... ELSE ...) when the THEN-only supertype and the (THENs + ELSE) supertype land in different ColumnDecimal storages -- for example THEN values (UInt16, Int8) with an ELSE of Decimal(9, 2). Closes #104335. #104378 (Groene AI).
• Internal failures reported via logExceptionBeforeStart (asynchronous insert flushes, materialized-view refreshes, parse errors raised during internal queries) now correctly increment the FailedInternalQuery, FailedInternalSelectQuery, and FailedInternalInsertQuery ProfileEvents alongside the user-visible FailedQuery, FailedSelectQuery, and FailedInsertQuery counters. Previously these internal counters stayed at zero for failures occurring before query execution started, undercounting a major class of internal failures. #104399 (Groene AI).
• Fix Code: 36. BAD_ARGUMENTS Expected literal, got {name:Type} thrown when a query parameter is used inside the base_backup setting of a BACKUP or RESTORE statement (e.g. BACKUP ... SETTINGS base_backup = S3({backup_name:String}, ...)). The regression was introduced in 26.1.5 by PR #99205. Closes #103324. #104413 (Groene AI).
• Fix a server abort in IcebergLocal/IcebergS3 writes when ALTER TABLE ... DROP COLUMN is followed by an INSERT with iceberg_metadata_staleness_ms greater than zero. ALTER now invalidates the local Iceberg metadata files cache so subsequent reads and writes see the new schema. #104419 (Groene AI).
• Fix DROP ROLE, DROP USER, DROP SETTINGS PROFILE, DROP ROW POLICY, DROP QUOTA and DROP MASKING POLICY to remove references to the dropped entity from any other access entity that referenced it (e.g. a user's DEFAULT ROLE list, a settings profile's TO list, a row policy's grantees) and persist the cleanup to disk. Previously the in-memory state appeared correct because SHOW CREATE filters unknown UUIDs, but the on-disk .sql files retained dangling ID('<dropped-uuid>') entries and the references were resurrected on the next server restart, surfacing as ACCESS_ENTITY_NOT_FOUND errors during distributed query execution. #104427 (Groene AI).
• Fixed a server abort triggered by azureBlobStorage, AzureBlobStorage-engine, and DeltaLake-on-Azure with a connection string whose BlobEndpoint URL has an empty, non-numeric, or out-of-range port (e.g. BlobEndpoint=http://host:abc/). The server now returns a clean BAD_ARGUMENTS error instead of aborting in debug/sanitizer builds. #104460 (Groene AI).
• Allow an unquoted identifier as the user name in the remote and remoteSecure table functions, mirroring how the database and table arguments accept unquoted identifiers. Previously such a query failed with a misleading authentication error referring to the default user. #104465 (Alexey Milovidov).
• Fixed Logical error: Incorrect ASTSelectWithUnionQuery (modes: M, selects: N) triggered when a SQL user-defined function body contains a parenthesized inner UNION ALL (e.g. CREATE FUNCTION f AS x -> (SELECT 1 UNION ALL (SELECT 1 UNION ALL SELECT 1))). #104477 (Groene AI).
• Fix uniqThetaIntersect returning the cardinality of the first argument instead of 0 when the second argument is an empty uniqTheta state -- for example the result of uniqThetaMergeStateIf(s, predicate) when the predicate excludes every row. #104529 (Groene AI).
• Fix SHOW TABLES and system.tables silently truncating the listing for DataLakeCatalog databases backed by Iceberg REST catalogs (iceberg-rest, onelake, biglake). When the catalog server paginates the list-tables or list-namespaces response (e.g. Microsoft Fabric / OneLake beyond ~50 tables per namespace), tables on later pages were silently invisible to SHOW TABLES and system.tables, even though they were queryable via direct SELECT. RestCatalog now follows the next-page-token continuation token defined by the Iceberg REST OpenAPI spec, matching the existing behavior of PaimonRestCatalog and UnityCatalog. #104531 (Groene AI).
• The input table function now infers its structure from the surrounding INSERT query's FORMAT clause when that format has a fixed schema (LineAsString, RawBLOB, JSONAsString, etc.), so users no longer have to repeat the structure as input('line String') for these formats. #104532. #104533 (Groene AI).
• Updated datatype of fields in Iceberg history from Int32 to Int64. Closes #94176. #104579 (Smita Kulkarni).
• Fixed Inconsistent AST formatting LOGICAL_ERROR when parsing a function call where a lambda follows a comma, e.g. SELECT substring(x, `x` -> `x`). The parser used to silently merge the preceding arguments into the lambda's left-hand side, producing a single-argument call that could not be re-parsed back to the same AST. It now preserves the function's original arity. #104626 (Groene AI).
• CHECK TABLE t now prefers a TEMPORARY table over a permanent one with the same name when no database qualifier is given, matching the precedence already used by SHOW CREATE TABLE, DESCRIBE TABLE, OPTIMIZE TABLE, and ALTER TABLE. Previously CHECK TABLE t skipped temporary tables entirely, so it failed with UNKNOWN_TABLE on a temporary Log or File table even though those engines support CHECK. Follow-up to #100966. #104637 (Groene AI).
• Fix Keeper termination and restart loop when get /keeper/availability_zone is sent with quorum_reads=true to a Keeper without <placement> configured. #104663 (myeongjun).
• Fix a TOCTOU data race in FutureSetFromTuple::buildOrderedSetInplace that results in a logical error. #104673 (Miсhael Stetsyuk).
• Fix several functions returning different results for the same input depending on whether arguments arrived as columns or constants: bitRotateLeft / bitRotateRight (boundary shift counts), length(FixedString) / concatWithSeparator with LowCardinality(Nullable) inputs, roundDown on NaN, and rightUTF8 on invalid UTF-8. #104710 (Raúl Marín).
• Fixed anyHeavy returning a non-heavy value when the most frequent value was the column default and the data lived across multiple MergeTree parts (sparse-column read path). #104712 (Raúl Marín).
• Fix several defects in setting-constraint handling: MergeTreeSettings constraints declared on a setting's canonical name could be bypassed by writing to an alias of that setting; the disallowed_values constraint check threw an exception on clamp paths (secondary queries, ON CLUSTER workers, SQL SECURITY DEFINER views) instead of silently dropping the change. #104737 (Raúl Marín).
• Fix a LOGICAL_ERROR exception (Metadata is not initialized) raised by OPTIMIZE TABLE, ALTER TABLE ... DELETE, ALTER TABLE ... ADD COLUMN and other ALTER variants on a lazily-attached Iceberg / IcebergLocal / DeltaLake / Hudi table whose metadata had not been loaded yet (typical after a server restart, or after a previous metadata write failed and left a corrupted metadata file on disk). The operation now either proceeds normally if the metadata loads successfully, or surfaces the underlying load failure as a regular user-facing exception instead of aborting the server in debug / sanitizer builds. #104738 (Groene AI).
• Fix segfault due to a use-after-free bug in AvroConfluentRowInputFormat. #104751 (Miсhael Stetsyuk).
• Scalar variants of numericIndexedVectorPointwiseMultiply, numericIndexedVectorPointwiseDivide, numericIndexedVectorPointwiseEqual, and numericIndexedVectorPointwiseNotEqual now raise INCORRECT_DATA when called with a UInt64 scalar above Int64::max. #104784 (FriendLey).
• Fix a bug where manually overriding a setting via its alias name (e.g. SET enable_analyzer = 1 instead of SET allow_experimental_analyzer = 1) after applying a compatibility setting could cause that override to be reverted by a subsequent change of the compatibility setting. #104829 (Raúl Marín).
• Fix AWS logger being disabled after https://github.com/ClickHouse/ClickHouse/commit/0e8ad4355c9d. #104837 (Konstantin Bogdanov).
• Fix three more functions returning different results for the same input depending on whether arguments arrived as columns or constants: transform (and caseWithExpression through it) with a constant Date/Date32/Enum/FixedString default, comparison operators between a String and a constant FixedString, and if/ifNull/nullIf with a FixedString branch under a constant condition. #104858 (Raúl Marín).
• Fix Bad cast from type DB::ColumnConst to DB::ColumnNullable server abort during partition pruning for MergeTree tables when the partition expression contains a function chain that collapses to a single constant value (such as floor(NULL, toRelativeYearNum(...))). #104861 (Groene AI).
• Fix a ThreadSanitizer data race in the ContextData copy constructor: table_function_results was copied from the source object without acquiring table_function_results_mutex, so a concurrent Context::executeTableFunction writer could race against the unsynchronized read in the copy constructor. #104879 (Groene AI).
• Fix data part consistency checks for types with dynamic structure and detect corrupted columns_substreams.txt. Resubmit of https://github.com/ClickHouse/ClickHouse/pull/103858 with additional changes. #104888 (Pavel Kruglov).
• Fix race between DROP and UNDROP in DatabaseCatalog. #104915 (Azat Khuzhin).
• Fix filesystem cache dynamic resize with partially downloaded segments, including restore accounting after failed eviction. #104921 (Antonio Andelic).
• DETACH TABLE on a temporary table (without the TEMPORARY keyword) now correctly raises SYNTAX_ERROR, matching the behavior of DETACH TEMPORARY TABLE. Previously it silently set an internal is_detached flag and returned without error. To remove a temporary table, use DROP TEMPORARY TABLE or DROP TABLE (the latter resolves the temporary table via Context::ResolveExternal). Closes #103475. #104943 (Groene AI).
• Make the filesystem table function honor max_memory_usage / max_server_memory_usage when loading file content. Previously, large or numerous parallel content reads could push past the limit without raising MEMORY_LIMIT_EXCEEDED and end up OOM-killed instead. #104956 (Alexey Milovidov).
• Fixed a LOGICAL_ERROR thrown when filtering system.detached_tables by uuid (e.g. SELECT count() FROM system.detached_tables WHERE uuid = '...'). The query now returns the expected result instead of aborting the server. #104979 (Groene AI).
• flattenTuple no longer raises a LOGICAL_ERROR when called on a tuple whose nested structure contains only empty Tuple() leaves (e.g. Tuple(c0 Array(Tuple())) or Tuple(c0 Tuple())). Such inputs now produce a user-facing ILLEGAL_TYPE_OF_ARGUMENT exception explaining that the flatten result would be an empty tuple. #104989 (Groene AI).
• Fix a server abort and a silent-wrong-result bug when querying loop(remote(...)) (or any loop() wrapping a storage that can defer aggregation) with GROUP BY. The outer planner used to add MergingAggregatedStep based on the inner storage's reported processing stage, but LoopSource always materialises its inner select with QueryProcessingStage::Complete and emits plain column chunks, so MergingAggregatedTransform tripped a LOGICAL_ERROR (Chunk info was not set for chunk in MergingAggregatedTransform) under enable_parallel_replicas = 1 and silently dropped the outer aggregation otherwise. #105001 (Groene AI).
• clickhouse-benchmark --reconnect (bare, no value) was inadvertently broken in 25.4 by a change that turned --reconnect into an integer option, requiring a value. The bare form now works again and is equivalent to --reconnect=1 (reconnect on every query). #105006 (Groene AI).
• Fixed malformed JSON output for column names ending with incomplete UTF-8 sequences. #105012 (Pablo Marcos).
• Fix silent data loss after EXCHANGE TABLES or CREATE OR REPLACE TABLE of a materialized view's source table. The MV's source-view dependency edge is now kept on the original name so it continues to fire on inserts. Regression introduced by #98779; restores the pre-regression behavior. #105029 (Sema Checherinda).
• Fix CANNOT_COMPILE_CODE Could not find symbol __fixunsdfti when JIT-compiling expressions that convert a Float to UInt128, such as toUInt128(<Float64 expression>). The unsigned 128-bit float-to-int compiler-rt builtins were missing from the JIT symbol resolver. Closes #105031. #105048 (Raúl Marín).
• Fix clickhouse-local not printing log messages from a failed query when send_logs_level is set. #105067 (Alexey Milovidov).
• Fix incorrect results when the same parameterized view is referenced more than once in the same query with different argument values. Previously, the analyzer collapsed the calls into one, silently dropping all but the first filter. #105170 (Alexey Milovidov).
• Fix TOTALS row being rendered twice at the bottom of the result table in the play.html web UI. #103803 (Alexey Milovidov).
• Reject non-finite vectors (NaN, ±Inf) during vector search (either as searched vectors or as reference vectors); they previously caused undefined behavior in usearch. #104079 (Groene AI).
• PromQL: fix the aggregation operator for empty vectors. #104425 (Vitaly Baranov).
• PromQL: fix error handling in the Prometheus query API. #104741 (Vitaly Baranov).
• Fix a race in MergeTreeTransaction::afterCommit where, after a connection loss between writing the commit CSN to ZooKeeper and finalizing the transaction, the COMMIT response could reach the client before the new creation_csn / removal_csn became visible in system.parts. #104708 (Tuan Pham Anh).
• Fix exponential memory growth in the KQL parser when converting nested array indexing (arr[arr[arr[...]]]). #105142 (Alexey Milovidov).
• Fix incorrect results for RIGHT ANY JOIN when the right table has multiple rows per key and the output block is split due to size limits. Closes #99431. #102064 (Vladimir Cherkasov).
• Check for stack overflow in Avro reader during nested-type deserialization. #102417 (Pavel Kruglov).
• Fix duplicate rows in system.completions for MergeTree settings — each setting name appeared twice because both getMergeTreeSettings and getReplicatedMergeTreeSettings were dumped despite having identical setting names. Closes #102013. #102015 (Groene AI).
• Fix StorageObjectStorageQueue (S3Queue, AzureQueue) blocking shutdown until partially-processed files were fully read from object storage. The source now aborts the read immediately on shutdown; deduplication ensures rows already streamed into the destination table before shutdown are not duplicated when the file is retried on next start. #103126 (Tuan Pham Anh).
• Fix multi-block inserts to the Alias table engine with insert_deduplication_token so that all blocks are kept. #103246 (Enric Calabuig).
• Fix JSONHas and JSONExtractBool on native JSON columns returning the extracted value (cast to UInt8) instead of 0/1. #103313 (zxuhan7).
• Protect the CustomSeparated input format against malformed or adversarial data that omits format_custom_row_after_delimiter. Header detection, schema inference, and variable-column rows previously accumulated fields unboundedly and could allocate many gigabytes of memory before failing. Reads now fail with INCORRECT_DATA once a single row contains more than 1,000,000 fields. #103404 (Groene AI).
• Fix RESTORE of replicated MergeTree tables so that restored part attachment uses backup_restore_keeper_max_retries instead of the regular insert Keeper retry budget. #104610 (Pablo Marcos).
• Fix wrong results from WHERE p AND <LowCardinality(Nullable(int)) constant> on MergeTree tables. Previously such queries returned zero rows because part pruning derived a NULL default from the LowCardinality(Nullable(...)) type and synthesized a notEquals(x, NULL) guard, pruning every part. #104767 (Groene AI).
• Fix incorrect aggregation result when grouping by a non-injective function of a column that is also the partition key (e.g. PARTITION BY a with GROUP BY intDiv(a, 2) or a % 2). Values from different partitions that mapped to the same group were not merged, producing duplicate group rows under allow_aggregate_partitions_independently = 1. #104869 (Nihal Z. Miaji).
• Fix a race in Keeper snapshot transfer where a snapshot could be removed or moved while it was being sent to a recovering follower. #104941 (Antonio Andelic).
• Fix a silent wrong-result bug in hilbertEncode and mortonEncode where a non-constant Tuple first argument (range mask) used row 0's values to drive the bit-shift for every row. The functions now compute the per-row mask values, so the result no longer depends on the input being constant or on the block size. #104992 (Groene AI).
• Fix clickhouse-local silently ignoring user-level configuration (profiles, users, quotas, access-control settings) when the configuration file is auto-discovered from ./clickhouse-local.xml, ~/.clickhouse-local/config.xml, or /etc/clickhouse-local/config.xml. Previously these settings were applied only when --config-file was passed or ./config.xml existed in the current directory; now all discovery paths behave consistently. #105008 (Groene AI).
• Fix BFloat16 columns silently returning zero matches when compared against a string literal (e.g. WHERE bf16_col = '49.9'). #105042 (Raúl Marín).
• Fix CLEAR COLUMN and TTL handling during merges for SummingMergeTree, AggregatingMergeTree, and CoalescingMergeTree when merge-required columns are absent or expired. Closes #101953. #105203 (Antonio Andelic).
• Fix a race between DNSCacheUpdater::run and Context::reloadClusterConfig by adding an explicit null-guard for shared->clusters_config before dereferencing it. #105220 (Mikhail f. Shiryaev).
• Fix best_effort date-time parsing for toDateTime64 with ms and ns precision. #105233 (Kaviraj Kanagaraj).
• Fix OSIOWaitMicroseconds reporting thread-lifetime I/O wait instead of per-query I/O wait. #105246 (Mikhail f. Shiryaev).
• Hudi table engine now raises INCORRECT_DATA (a regular query-level exception) instead of LOGICAL_ERROR when a parquet file in the table directory does not match the Hudi [FileId]_[FileWriteToken]_[Timestamp].[extension] naming convention. Previously such file names caused an exception in debug builds. #105266 (Groene AI).
• Fix deadlock in ParallelFormattingOutputFormat on schedule failure: when scheduleFormatterThreadForUnitWithNumber throws (e.g. CANNOT_SCHEDULE_TASK), the unit was left in READY_TO_FORMAT with no formatter thread to process it, leading to a hang. The schedule call is now wrapped in try/catch and any failure is routed through onBackgroundException so the collector exits cleanly. #105275 (Azat Khuzhin).
• Fix silent data loss in Distributed async inserts when recovering from an abnormal shutdown: if the last .bin file in a saved batch was intact but a middle one was corrupted, DistributedAsyncInsertBatch::recoverBatch would only validate the last file's header and then sendBatch would mark the entire batch — including the intact files — as broken, losing their rows. Each file's header is now validated individually so only the actually broken file is moved to broken/ and the surviving rows reach the remote shard. #105281 (Groene AI).
• Fix a regression in clickhouse extract-from-config --try: when the config used from_env attributes and had no include_from element (or had one pointing to a missing file), all from_env substitutions were silently dropped and returned empty strings. This broke the Docker entrypoint port discovery in 26.2.5. Closes #101704. #105283 (Groene AI).
• Fix INSERT INTO a SQLite table failing with a SQLite syntax error when the inserted value is an Enum, JSON, or AggregateFunction whose text representation contains a single quote. The output_format_values_escape_quote_with_quote setting is now honored by the corresponding serializations (previously only String and FixedString honored it). #105285 (Groene AI).
• Fix Code: 44. ILLEGAL_COLUMN: Cannot add column ...: column with this name already exists thrown by distributed queries with allow_push_predicate_ast_for_distributed_subqueries = 1 (the default) when a GLOBAL IN tuple is matched against a subquery whose projection contains duplicate column names, e.g. (x, y) GLOBAL IN (SELECT number, number FROM numbers(5)). #105290 (Groene AI).
• Fix reinterpret to Array(LowCardinality(...)) returning a confusing NOT_IMPLEMENTED error at runtime; it now returns ILLEGAL_TYPE_OF_ARGUMENT during type checking. #105301 (Raúl Marín).
• minMap/maxMap (array form) and minMappedArrays/maxMappedArrays now treat NaN consistently with ORDER BY: NaN is treated as last (returned only when all values are NaN). Previously, results depended on the position of NaN in the data due to IEEE 754 unordered comparison semantics, and disagreed with the Map-argument form of minMap/maxMap that was fixed in #100448. #105331 (Raúl Marín).
• Fix a memory leak in the per-table ColumnsDescription cache for MergeTree-family tables with Nested columns. Entries were never evicted across ALTER ADD COLUMN/DROP COLUMN cycles when share_nested_offsets = 1 (the default). #105376 (Groene AI).
• Fix BAD_ARGUMENTS exception "It's a bug! Only integer types are supported by __bitWrapperFunc" thrown when a SELECT with a TYPE set(N) skip index has a WHERE atom whose result type is Float, BFloat16, or any other non-integer type (for example WHERE c0 + 0.1 or WHERE log(c0)). The skip index now falls back to the regular filter path in that case. #105384 (Groene AI).

Build/Testing/Packaging Improvement

• Stop using the system compiler-rt libraries and headers. Closes #91475. #102857 (Konstantin Bogdanov).
• Refresh the distroless Docker base image to fix OpenSSL CVEs in libssl3t64. #103583 (Rahul Nair).
• Reliably receive the GPG key during releases by chaining multiple Ubuntu keyservers, instead of timing out on keyserver.ubuntu.com. #103834 (Mikhail f. Shiryaev).
• Remove and forbid build-time CMake checks (check_*, try_compile, try_run). The compiler and toolchain are fixed, so feature detection at configure time is unnecessary and is now blocked project-wide; any version-specific behaviour must be gated on CMAKE_CXX_COMPILER_VERSION explicitly. #103980 (Alexey Milovidov).
• Bump libarchive from 3.8.6 to 3.8.7. #104047 (Robert Schulze).
• Update mongo-c-driver to 2.3.0. #104300 (Raúl Marín).
• Update LLVM dependencies for 22.x. #104381 (Joshua Carp).
• Make the embedded-client and PTY descriptor classes build on macOS and FreeBSD by using portable POSIX posix_openpt / grantpt / unlockpt and removing Linux-only #if guards. #104436 (Alexey Milovidov).
• Upgrade librdkafka to version 2.14.1. #105222 (János Benjamin Antal).

ClickHouse release 26.4, 2026-04-30. Presentation, Video

Backward Incompatible Change

• The IN operator now uses exact value semantics for Bool type: only 0 and 1 values in the set match Bool values. Previously, numeric values greater than 255 in the IN set were incorrectly clamped to true when compared against Bool, so SELECT CAST(1, 'Bool') IN (256) returned 1. Now it correctly returns 0. Closes #92980. #93115 (Ashrith Bandla).
• The H3 library has been updated to v4, which improves the precision of length, area, and other metric calculations. This change is backward incompatible because the new results differ from previous ones. #100348 (Alexey Milovidov).
• Disallows using SELECT as a bareword identifier in a WITH expression list element. #101059 (Aruj Bansal).
• This patch changes how the merge table will handle virtuals. If the underlying table contains _table or _database, these columns will be read from storage; otherwise, they will be filled after the read step using the expression step. #101742 (Mikhail Artemenko).
• The IN operator now rejects lossy Decimal conversions inside composite types (Tuple, Array, Map) as well, making its behavior consistent with top-level scalar comparisons. Previously, precision checks were enforced only for top-level scalar values: for example, CAST('33.3', 'Decimal64(1)') IN (33.33) correctly returned 0, but CAST(['33.3'], 'Array(Decimal64(1))') IN ([33.33]) incorrectly returned 1 because the lossy conversion happened inside an Array. Now both cases correctly return 0. #101812 (Nihal Z. Miaji).
• Reduced default http_max_fields from 1,000,000 to 1,000 and http_max_field_name_size from 128 KB to 4 KB to limit pre-authentication memory usage by HTTP connections. Added http_max_request_header_size and http_headers_read_timeout settings. Users who rely on the previous higher limits can restore them via settings. #103285 (Sema Checherinda).

New Feature

• Add automatic spilling to hash and parallel hash joins by converting them to grace hash join when memory limit is reached. This behavior is controlled by max_bytes_before_external_join. #97813 (János Benjamin Antal).
• Add Arrow Flight SQL support. #91170 (Yakov Olkhovskiy).
• Add incremental read support for Paimon table engines with Keeper-backed snapshot progress tracking, including targeted snapshot delta reads via paimon_target_snapshot_id, and extend test coverage for type mapping, partition pruning, and incremental read scenarios. #93655 (XiaoBinMu).
• The stem function is now non-experimental (previously, setting allow_experimental_nlp_functions had to be enabled). #102399 (Jimmy Aguilar Mena). You can now stem all the words/tokens in columns String, FixedString, Array([Fixed]String), Nullable, LowCardinality and Const easily with the stem function. #99137 (Jimmy Aguilar Mena).
• Implement new behavior of max_insert_block_size_rows, max_insert_block_size_bytes, min_insert_block_size_rows, min_insert_block_size_bytes in squashing under compatibility setting use_strict_insert_block_limits. #94207 (Kirill Kopnev).
• Add function arrayAutocorrelation(arr [, max_lag]) that computes the normalized autocorrelation of a numeric array for each lag. Supports integer, float, and decimal array types. #94776 (Wenyu Chen).
• A SQL function obfuscateQuery. Closes #98010. #98305 (Xuewei Wang).
• Add support for Map and JSON/Object types as dictionary attributes. Now dictionaries can store and retrieve complex types including Map(String, String), Map(String, Array(String)), JSON, and Nullable(JSON) types in both FLAT and HASHED layouts. #98627 (yanglongwei).
• Added two new MergeTree settings — replicated_fetches_min_part_level and replicated_fetches_min_part_level_timeout_seconds — that allow replicas to skip fetching freshly-inserted (unmerged) parts from peers, reducing replication overhead during heavy ingestion. #98625 (tanner-bruce).
• Add MergeTree skip index support for JSON columns using JSONAllPaths with bloom_filter, tokenbf_v1, ngrambf_v1, and text (inverted) index types, enabling granule skipping based on the set of JSON paths present in each granule. #98886 (Pavel Kruglov).
• The printf function now supports non-constant format strings, allowing different format patterns per row based on column values. #98991 (Yash ).
• Add a new projection index, commit_order, that reorganizes data in insertion order. #99004 (Mikhail Artemenko).
• Add highlight function that wraps occurrences of search terms in a text string with HTML tags (default <em>/</em>). Supports ASCII case-insensitive matching, automatic merging of overlapping matches, and custom open/close tags. #99131 (Peng).
• Implement quotas by normalized query hash to protect public ClickHouse services from abuse. 1. Support NORMALIZED_QUERY_HASH as a quota key type - separate quota buckets per unique normalized query, so CREATE QUOTA q KEYED BY normalized_query_hash tracks each distinct query independently. 2. Support QUERIES_PER_NORMALIZED_HASH as a quota resource type -- limits max executions of any single normalized query within an interval, so MAX queries_per_normalized_hash = 100 prevents any one query pattern from running more than 100 times. #99586 (Alexey Milovidov).
• Users can now write join queries using the NATURAL JOIN syntax, which automatically matches on all columns sharing the same name and deduplicates those columns in the result. #99840 (Peter Nguyen).
• Support SET TIME ZONE 'tz' as alias for SET session_timezone. #99883 (phulv94).
• Added support for parameterized queries in the Web UI (play.html): query parameters like {name:Type} are detected and input fields are shown for filling in their values. #100041 (Alexey Milovidov).
• Support SQL standard VALUES clause as a table expression in FROM, e.g. SELECT * FROM (VALUES (1, 'a'), (2, 'b')) AS t(id, val). #100143 (Desel72).
• Add PostgreSQL-compatible units to the EXTRACT operator: EPOCH, DOW, DOY, ISODOW, ISOYEAR, WEEK, CENTURY, DECADE, MILLENNIUM. Also fix EXTRACT(WEEK FROM date) which previously threw an error. #100274 (Alexey Milovidov).
• Added support for SQL-standard compound interval literals with TO range qualifiers, e.g. INTERVAL '1:30' HOUR TO MINUTE. Internally decomposed into sums of intervals. #100453 (Desel72).
• Add asynchronous metrics for kernel TCP receive and transmit buffer memory (sk_rmem_alloc, sk_wmem_alloc) of HTTP connection pool sockets, reported as p50/p75/p90/p95 percentiles and totals per connection group. #100575 (Sema Checherinda).
• Added a jemalloc profiling web UI for ClickHouse Keeper, available at /jemalloc on the HTTP control port. #100606 (murphy-4o).
• Implement command SYSTEM FLUSH OBJECT STORAGE QUEUE db.table PATH 'x' for ordered and unordered modes. #100709 (Bharat Nallan).
• Added function JSONAllValues that returns all values from a JSON column as Array(String), with values serialized in text representation and ordered by their path names. Added support of text index for JSONAllValues expression on JSON columns. When a text index is created on JSONAllValues(json_column), it is automatically used to filter queries on JSON subcolumns (e.g., json_column.key1 = 'value'). #100730 (Anton Popov).
• Adds a new setting input_format_column_name_matching_mode which allows different case sensitivities for input formats. #99346 (manerone).
• Add watch command to clickhouse-keeper-client with watch support in get, exists, and ls commands. #100834 (Den Kalantaevskii).
• Added getChildrenRecursive (ListRecursive) request to ClickHouse Keeper and lsr command to clickhouse-keeper-client. This closes #99916. #100998 (Konstantin Vedernikov).
• Add new function arrayTranspose taking a two-dimensional array (matrix) and transposing it: SELECT arrayTranspose([[1, 2, 3], [4, 5, 6]]). #101214 (Vitaly Baranov).
• auto_statistics_types mergetree setting defaults to 'minmax, uniq' — minmax and uniq statistics are created automatically for all suitable columns in new tables - materialize_statistics_on_insert defaults to false — statistics are now built during merges rather than at insert time, reducing insert overhead. use SET materialize_statistics_on_insert = 1 to restore the old behavior. #101275 (Han Fei).
• Add prefer_dependency_replica refresh setting for materialized view dependency chains to reduce missing data from cross-replica replication lag. #101591 (Seva Potapov).
• Adds a hasPhrase (alias matchPhrase) function for phrase search (continuous sequences of tokens). Search is brute-force, i.e. not supported by the text index yet. #101997 (Elmi Ahmadov).
• Add s3_read_request_duration_microseconds and s3_read_request_bytes histogram metrics to observe S3 GET request connection lifetime and bytes consumed, visible in system.histogram_metrics and the Prometheus endpoint. #102058 (Sema Checherinda).
• Date and Date32 values can now be added to Time and Time64 values using the + operator, producing a DateTime or DateTime64 result. For example, SELECT toDate('2024-01-15') + toTime('14:30:25') returns 2024-01-15 14:30:25. The result is computed in the session timezone, and out-of-range results are handled according to the date_time_overflow_behavior setting. Closes #95914. #102421 (Nihal Z. Miaji).
• The text index is now GA and stays enabled regardless of the compatibility setting, preventing unexpected disabling during backup restores or when running in compatibility mode. #101518 (Nikita Fomichev).

Experimental Feature

• Add ALTER TABLE ... EXECUTE remove_orphan_files for Iceberg tables to identify and remove unreferenced files from object storage. #99127 (murphy-4o).
• Add query_plan_optimize_join_order_randomize setting that randomizes statistics used for join reordering, useful for testing. #100643 (Vladimir Cherkasov).
• Add AI function support to ClickHouse, allowing users to call OpenAI and Anthropic endpoints using SQL. aiGenerate is included as the first such function. #100831 (George Larionov).
• Add AI functions: aiClassify, aiExtract, and aiTranslate for utilizing LLM APIs in ClickHouse. #100832 (George Larionov).
• Added system.histogram_metric_log, a new system table that periodically snapshots all histogram metrics (e.g. S3/Azure latencies, keeper request processing stages durations). Also, the value column of system.histogram_metrics changes to Float64 as it's more flexible and compatible with the Prometheus data model. #103046 (Miсhael Stetsyuk). The table structure is likely to be changed in future releases.

Performance Improvement

• ClickHouse is now able to prune entire data parts in SELECT queries based on min/max statistics. #94140 (zoomxi).
• Reduce lock contention during readonly operations on ReplicatedMergeTree tables with finished mutations. #95771 (Eduard Karacharov).
• Respect optimize_read_in_order when reading projections. Closes #89453. #95885 (Andrey Zvonov).
• Small set of improvements in Hash Join and Concurrent Hash Join. #96663 (Yarik Briukhovetskyi).
• Optimize DISTINCT transform by disabling LowCardinality columns optimization when input data is almost distinct. #97113 (Nihal Z. Miaji).
• Performance optimization for LIKE queries from #97723. Now these queries can use text indices. #98149 (Elmi Ahmadov).
• Vectorized math functions (exp, log, sigmoid, tanh) are now accelerated on AArch64 (using NEON/SVE) and on FreeBSD/Darwin, where they previously used a slower scalar fallback. #98230 (Raúl Marín).
• Queries filtering on MergeTree primary key columns with regexp alternations over literal strings, such as ^(abc-1|abc-2), can now use primary key pruning when the alternatives share a common prefix. #98988 (Yash ).
• Generalize ORDER BY ... LIMIT top-k dynamic filtering to support Nullable, String, and COLLATE types. #99033 (murphy-4o).
• Speedup hash join on Int32 and Int64 keys with small range by using a direct-index hash table. #99275 (Hechem Selmi).
• Faster discontinuous queries for LowCardinality columns with a single dictionary. #99285 (Ivan Babrou).
• Speed up var*Stable and stddev*Stable functions for Float64 columns by devirtualizing the inner loop. Note: this enables compiler optimizations (FMA/registers) that alter floating-point results at the ULP level. #99460 (Riyane El Qoqui).
• Use optimised Firedancer base58 encode for inputs of 32/64 bytes (automatic for base58Encode). Allow using optimised base58 decode if decoded result is 32/64 bytes (explicit with base58Decode('...', 32) or alike). #99461 (Joanna Hulboj).
• Enable linker section-based optimizations (-ffunction-sections, -fdata-sections, --icf=all) to reduce binary size and improve instruction cache utilization. #99474 (Alexey Milovidov).
• Fix negative scaling for short queries with aggregation on machines with many cores. When a query reads few marks, the pipeline no longer expands to max_threads after aggregation, avoiding overhead from mostly-empty streams. #99493 (Alexey Milovidov).
• Improve the performance of queries with parallel replicas by correctly selecting the reading task size. #99801 (Nikita Taranov).
• Allow prefetching when reading a remote file through the userspace page cache. #99919 (Alexey Milovidov).
• Avoid unnecessary computation of String .size subcolumn during subcolumns enumeration. #99941 (Pavel Kruglov).
• Make clickhouse-client's progress bar less jittery when working from a hotel with clusters with a very large number of replicas. #100145 (Alexey Milovidov).
• Start MemoryWorker in clickhouse-local when page cache is enabled, so that the userspace page cache can be actually used. #100306 (Alexey Milovidov).
• Optimize queries by pushing the LIMIT clause down into the UNION ALL. #100364 (Alexey Milovidov).
• Add JIT compilation support for String and FixedString column comparisons in ORDER BY, improving merge-phase sort performance by 6–17% for string-heavy sort keys. Co-authored with @lgbo-ustc. #100577 (Raúl Marín).
• When read_in_order_use_virtual_row is enabled together with the new read_in_order_use_virtual_row_per_block setting, virtual row boundary information is now emitted after each block read from MergeTree, allowing the merge to reprioritize sources mid-stream for parts whose data is fully filtered out by WHERE/PREWHERE/JOIN. Close #99945. #100603 (Vladimir Cherkasov).
• Faster Float-to-String conversion for large integer values by extending the itoa fast path with dragonbox-compatible rounding. #100649 (Raúl Marín).
• Replace dragonbox with zmij for 1.5x-3x faster Float-to-String conversion. #100650 (Raúl Marín).
• Faster Int128/UInt128 to string conversion by replacing software division with Barrett reduction and unrolling the conversion loop. #100671 (Raúl Marín).
• Avoid spawning redundant threads in uniqExact parallel merge. #100686 (Jiebin Sun).
• Add batch parallel merge for uniqExact. #100687 (Jiebin Sun).
• Better parallelization of queries with simple views (with underlying MergeTree table) executed with parallel replicas. #100815 (Igor Nikonov).
• Implements support of parallel replicas over simple views (including eligible UNION ALL views over MergeTree tables) when parallel_replicas_allow_view_over_mergetree=1. This allows to parallelize view's outer query instead of inner one which increases query parallelization across nodes. #100958 (Igor Nikonov).
• Optimise reading in order of the primary key for full_sorting_merge when filters with IN are present in the query plan. #101261 (Nikita Taranov).
• Optimization allocations/deallocations by caching sampling settings instead of traverse all memory tracker hierarchy. #101267 (Azat Khuzhin).
• Fix significant INSERT performance regression when deduplicate_insert = 'enable' (default since 26.2) by deferring data hash computation from squashing to the sink and using batch column hashing via updateHashWithValueRange, reducing overhead from ~2.5s to ~0.5s for 5M rows with 22 columns. #101494 (Sema Checherinda).
• Reduce profiled lock overhead by using try_lock to avoid timing uncontended acquisitions and removing hold-time measurement. #101502 (Antonio Andelic).
• Replace hand-written AVX-512 intrinsics in arrayDotProduct with platform-independent auto-vectorizable loops, adding AVX2 and ARM NEON support. #101571 (Peng).
• Improve performance in INSERT VALUES for Map, Array, and Tuple columns when values are passed as escaped strings (e.g. '{\'key\':1}'), avoiding unnecessary fallback to the SQL expression parser. #102119 (Joanna Hulboj).
• Fixed excessive RabbitMQ table engine CPU usage. #102711 (Jaap Elst).
• The JOIN order optimizer now infers transitive equi-join predicates from existing join conditions. For example, given A.x = B.x AND B.x = C.x, the equivalence A.x = C.x is recognized, allowing the optimizer to consider direct joins between transitively-connected tables. This can improve plan quality for star and snowflake schemas where dimension tables connect through a shared fact table. The feature is controlled by the new enable_join_transitive_predicates setting (off by default). #98479 (Alexander Gololobov).
• Optimize TRUNCATE DATABASE TABLES LIKE by pre-cancelling merges in parallel. #98597 (Shaohua Wang).
• Add monotonicity support for multiply, enabling primary key pruning for key * constant expressions. #98983 (Amos Bird).
• Cache dictionaries no longer take an exclusive lock in hasKeys; this reduces lock contention by using a shared lock for cache reads. #100796 (liuguangliang).
• Inline VIEW subquery in the query tree to allow more optimisations to be applied to the VIEW. #100830 (Dmitry Novik).
• Optimize cache loading on server startup. #101500 (Kseniia Sumarokova).
• Implement lazy column materialization for ReplacingMergeTree with FINAL in case the predicate is selective enough. #101647 (Nikolai Kochetov).
• Re-enable the optimize_rewrite_array_exists_to_has optimization (off by default since 23.10). It rewrites arrayExists(x -> x = elem, arr) into the much faster has(arr, elem) and now correctly skips the rewrite when the array element type and elem are not compatible for has (e.g. Date vs String), so previously breaking queries continue to work. Closes #71431. #100944 (Alexey Milovidov).

Improvement

• Improved EXPLAIN PLAN pretty=1 output: print top-level query output columns, show join relation labels/symbols with estimated result rows and locality, and include per-step output columns for join/source steps. The changes cover Information Deficit part from #98117. #99462 (Kirill Kopnev).
• Add MergeTree table setting share_nested_offsets (default true). When set to false, Array columns with dotted names (e.g. n.a, n.b) are treated as independent columns instead of sharing offset files and validating equal array sizes as part of legacy Nested semantics. #98416 (Amos Bird).
• Users can now specify multiple authentication methods in users.xml/yaml configuration (in SQL it was always possible). #91998 (Flip-Liquid).
• Auto reload Raft inter-node connections which are using TLS. #93455 (Evgeny).
• Extend cast_keep_nullable to work with Dynamic/JSON types. When set, casting NULL from types that can be Nullable will return NULL, otherwise NULL will throw CANNOT_INSERT_NULL_IN_ORDINARY_COLUMN error. #96504 (Seva Potapov).
• Reduced the memory footprint from the internal data structures (ISerialization objects) by introducing an object pool. #96563 (Nikita Mikhaylov).
• Add support of password and identity fields to keeper-client XML config. #96800 (Grigorii Sokolik).
• Improve Iceberg writes for the unity catalog. #98162 (Konstantin Vedernikov).
• Add setting finalize_projection_parts_synchronously to allow synchronous finalization of projection parts during INSERT, reducing peak memory usage for tables with many projections while preserving existing async behavior by default. #98228 (Amos Bird).
• Add projections_duration_ms column to system.part_log that records per-projection merge/rebuild duration in milliseconds. #98292 (Amos Bird).
• Improve canceling queries using ExpressionTransform and NumbersRangedSource by KILL QUERY and cancel query (Ctrl+C) in clickhouse-client. #98908 (Roman Vasin).
• Replace the hardcoded source_table_engines list with a runtime lookup via StorageFactory::getAllStorages(). This adds access checks for some missing table engines and closes #71544. #98984 (pufit).
• Add a setting to control type mismatch behavior for Variant and Dynamic (throw or return null). #99085 (Bharat Nallan).
• Improve Iceberg and Spark compatibility: fix inconsistent path handling caused by mixed usage of storage paths and metadata paths; enforce that Iceberg tables write down a table location that is either a URL or an absolute path; add a fallback for counting file sizes in Azure because some ClickHouse readers don't support byte counting after traversal; handle version-hint.txt in a manner compatible with Spark; introduce type-level abstractions that make it harder to mix up path types in the future; add tests for Azure and Local that verify cross-engine interoperability without intermediate uploading/downloading; fix usage of position deletes, which previously relied on path inference heuristics where that approach is inappropriate. #99163 (Daniil Ivanik). #100420 (Daniil Ivanik).
• Fix possible race condition in IPartitionStrategy::cached_result introduced in https://github.com/ClickHouse/ClickHouse/pull/92844. #99400 (Arthur Passos).
• Users can now write ClickHouse Interval datatypes in the Arrow Format. #99519 (Peter Nguyen).
• Adds native support for importing and exporting UUID data types in Arrow and Parquet formats. Users can now directly query and transfer UUID data between ClickHouse and other data tools without requiring manual string conversions or workarounds. Automated logical inference for top-level UUIDs, and support for explicit schema hint for nested UUIDs. #99521 (Ivan).
• Support 7z archives on object storage. Closes #70968. #99600 (Alexey Milovidov).
• Add ObjectStorageListedObjects, ObjectStorageGlobFilteredObjects, ObjectStoragePredicateFilteredObjects, and ObjectStorageReadObjects ProfileEvents for introspection of object storage (S3, Azure, etc.) file listing and reading pipeline. #99778 (Sema Checherinda).
• Fix merge table function failing with UNKNOWN_IDENTIFIER error when querying columns not present in all underlying distributed/remote tables. #99833 (Alexey Milovidov).
• Now we include commit time in total mutation execution time metric for ReplicatedMergeTree. It was lost after #96376. #99936 (alesapin).
• Add a write-ahead log for blob objects pending removal in MetadataStorageFromDisk, improving durability and consistency between metadata and remote object storage when objects are deleted. #100019 (Maksim Kita).
• Disable AI SQL generation (?? command) in the embedded client (SSH and WebSocket protocols) to prevent access to the server's environment variables. #100290 (Alexey Milovidov).
• Change the interface for Iceberg inserts with the catalog. Deprecate settings: storage_catalog_type, storage_aws_access_key_id, etc. #100334 (Konstantin Vedernikov).
• Render tabs as 4 spaces when pasting into clickhouse-client. Closes #100405. #100416 (Raúl Marín).
• Avoid scanning the whole remote data lake catalog for “Maybe you meant …” table hints when show_data_lake_catalogs_in_system_tables is disabled. #100452 (Alsu Giliazova).
• Apply distributed_index_analysis_min_indexes_bytes_to_activate after partition pruning. #100477 (Azat Khuzhin).
• Fix assertion failure in Parquet bloom filter push down when using empty IN/NOT IN clauses. #100543 (zoomxi).
• MinMax column statistics now store the minimum and maximum values as Field (typed) instead of Float64. The serialized format includes the column type name alongside the values. The statistics file version is bumped to V2; files written by older versions require re-materialization (ALTER TABLE … MATERIALIZE STATISTICS ALL). fix #53140. #100605 (Han Fei).
• Update cppkafka to include fix for Consumer close deadlock. #100612 (Azat Khuzhin).
• Object information used for parsing data files in Iceberg now contains the number of file rows and file size in bytes parsed from manifest file. #100645 (Daniil Ivanik).
• Add use_separate_cache_arena configuration parameter to be able to control separation of the cache memory arena. #100664 (Seva Potapov).
• Adds native support for importing Apache Arrow's StringView and BinaryView data types into ClickHouse String columns, improving compatibility for Arrow-based ingestion. #100762 (Ivan).
• A few Keeper server settings are now hot-reloaded if config file is changed at runtime: max_requests_batch_size, max_requests_batch_bytes_size, max_request_size, quorum_reads. #100773 (Michael Kolupaev).
• Increment profile events MemoryAllocatedWithoutCheck/MemoryAllocatedWithoutCheckBytes in release build. #100899 (Pavel Kruglov).
• Cgroupv2 memory tracking now excludes slab_reclaimable from kernel memory, giving a more accurate measure of non-reclaimable memory usage. #100901 (Antonio Andelic).
• use_partition_pruning = 0 now also disables MinMax index pruning and count optimization on partition key columns, in addition to disabling pruning based on partition keys. #100904 (Nihal Z. Miaji).
• pretty=1 in EXPLAIN [PLAN] now prints expressions in a human readable format. #100927 (Kirill Kopnev).
• accurateCastOrNull and accurateCastOrDefault now support Tuple target types, including nested Tuples with Nullable elements. Previously these functions rejected Tuple targets because Tuple could not be inside Nullable. Closes #100820. #100942 (Nihal Z. Miaji).
• Fix chart duplication in Play UI when switching between light and dark themes. #101058 (Alexey Milovidov).
• Update chdig to v26.3.1 (perfetto UI, sparklines to summary for CPU/Memory/Merges/Queries), system.warnings, regexp search in logs). #101092 (Azat Khuzhin). Update chdig to v26.4.3 (perfetto improvements, fixes for sharing via pastila.nl, flamegraph diffs, change settings in realtime). #103145 (Azat Khuzhin).
• You can now have a trailing comma in the WITH clause before a SELECT query. #101093 (Aruj Bansal).
• Add compress_per_column_in_compact_parts MergeTree setting to control how compressed blocks are organized within Compact parts. When true (default, preserving current behavior), each column starts a new compressed block, allowing selective decompression. When false, all columns within a granule are packed into the same compressed block, improving compression ratio and read performance for workloads that always read all columns. #101114 (Amos Bird).
• Show table info balloon in Play UI only when hovering over the table name, not the entire row. #101118 (Alexey Milovidov).
• Add engine-specific icons and improve table list UX in the Play UI sidebar. #101134 (Alexey Milovidov).
• Support Nullable(Tuple) for Arrow, ArrowStream, ORC, legacy Parquet formats. #101272 (Nihal Z. Miaji).
• Display TOTALS row as a table footer in the web UI (play.html). #101286 (Alexey Milovidov).
• Support multi-query mode in the web UI (play.html): run multiple queries at once with parallel execution of SELECT-like queries and per-query result display. #101290 (Alexey Milovidov).
• Fix column resize in play.html web UI after the result table was refactored into a web component. #101295 (Alexey Milovidov).
• Add ability limit amount of jemalloc profile flushes on MEMORY_LIMIT_EXCEEDED per time interval. #101396 (Azat Khuzhin).
• Added keeper settings nuraft_streaming_mode (by default false), nuraft_max_log_gap_in_stream, nuraft_max_bytes_in_flight_in_stream. Closes #90743. #101427 (Kseniia Sumarokova).
• Added CGroupMemoryUsedWithoutPageCache async metric that reports cgroup memory usage excluding both the kernel OS page cache and the ClickHouse userspace page cache, mirroring MemoryResidentWithoutPageCache. Also clarified the CGroupMemoryUsed metric description. #101513 (Francesco Ciocchetti).
• Add parser-level syntactic sugar for the SQL standard OVERLAY function syntax. The overlay function already exists; this adds support for the keyword-based form using PLACING, FROM, and FOR as separators. #101681 (Desel72).
• Added column alias INDEX_LENGTH to system table information_schema.tables, analogous to existing uppercase aliases in this table. #101705 (Robert Schulze).
• System table information_schema.tables now ignores inactive table parts. This makes the shown table size values more realistic. #101706 (Robert Schulze).
• The ngrams function now rejects invalid ngram lengths. Example: SELECT ngrams('abc', 0) now returns an error. #101922 (Robert Schulze).
• A follow-up for #91820 and #90837: filter unsupported algorithms from the error message; run FIPS-specific tests in FIPS builds. #102067 (Mikhail f. Shiryaev).
• Limit cell height to three lines in the Web UI (play.html), with expandable cells on click. #102154 (Alexey Milovidov).
• Added new option that allows to force (virtual/path) style for S3 endpoints. Resolves #82019; #76007 Continue of https://github.com/ClickHouse/ClickHouse/pull/83168. #102378 (Konstantin Vedernikov).
• The restore_replace_external_engines_to_null setting now also skips restoring databases with external engines (e.g. DataLakeCatalog, MySQL, PostgreSQL, S3) instead of failing or initiating external connections. #102400 (Nikita Fomichev).
• Add text index analysis support for the hasPhrase function via the HINT mode. #102438 (Elmi Ahmadov).
• Treat STATISTICS as read-only in ColumnDependency to fix LOGICAL_ERROR during MATERIALIZE STATISTICS ALL. #102627 (Konstantin Bogdanov).
• Create and populate system.asynchronous_metric_log in keeper-as-server mode. #102664 (Miсhael Stetsyuk).
• Add default_system_log_flush_policy.skip_alias_columns config option to allow omitting ALIAS columns from system log tables, fixing S3-backed system logs that reject ALIAS columns. #102669 (Miсhael Stetsyuk).
• Don't enable auto statistics for system tables. They rarely have chance to use them. #102862 (Han Fei).
• Support array tokenizer for the LIKE optimization. #102880 (Elmi Ahmadov).
• Send MemoryAllocatedWithoutCheck even in release builds. #103064 (Azat Khuzhin).
• Expose per-thread untracked_memory in system.stack_trace. #103065 (Azat Khuzhin).

Bug Fix (user-visible misbehavior in an official stable release)

• Fix Block structure mismatch in stream error caused by unnecessary columns returned from Lazy materialization. Fixes #95191. #96682 (Nikolai Kochetov).
• Fix a logical error with data masking policy query with ON CLUSTER. #97594 (Bharat Nallan).
• Fix a bug when using Unity catalog on top of GCS. #98456 (Melvyn Peignon).
• DataLakeCatalog now respects the server's http_forbid_headers configuration when validating the auth_header setting. #98827 (Michael Anastasakis).
• Fix N+1 HeadObject calls for S3 brace-expansion globs. #99219 (Konstantin Bogdanov).
• Validate setting changes in create queries when the engine itself also supports settings. #99279 (János Benjamin Antal).
• Fixed ALTER TABLE UPDATE/DELETE failing with Missing columns error when a table has a MATERIALIZED column whose expression depends on an EPHEMERAL column. #99281 (Yash ).
• Credentials in JDBC, ODBC, and NATS connection strings are now masked in query logs and SHOW CREATE output, preventing accidental exposure of sensitive information. For URI-style connection strings (e.g. {scheme}://{user}:{password}@{host}), only the password portion is masked while the rest remains visible for easier debugging. The nats_token setting is now also masked. #99344 (János Benjamin Antal).
• Fix parseDateTimeBestEffort incorrectly parsing words starting with month prefixes in DD-month-YYYY format. Closes #99345. #99350 (Pavel Kruglov).
• Fix ignoring of TABLE_UUID_MISMATCH for non analyzer. #99380 (Azat Khuzhin).
• Fix a bug where explicit settings sent alongside compatibility in the same request could be silently ignored when their value matched the server default. #99402 (Raufs Dunamalijevs).
• Fixes cases where numbers with leading zeros in hive partitioning path were causing errors. Fixes #98801. #99458 (Yarik Briukhovetskyi).
• Fix heap-use-after-free when a table is dropped concurrently with a running read query (19 occurrences in CI over the last 90 days). #99483 (Alexey Milovidov).
• Fixed a bug in Keeper where a read request could get stuck (causing session to time out) if a different unrelated session on the same server was closed at just the wrong moment. #99484 (Michael Kolupaev).
• Validate column structure before applying patches. #99531 (Seva Potapov).
• Fix vertical merge rows_sources assertion failure when SYSTEM STOP/START MERGES toggles rapidly during merge of table with Dynamic columns. #99532 (Alexey Milovidov).
• Fix incorrect partition pruning for toWeek() that caused queries with WHERE toWeek(date, mode) = N to return empty results for weeks 49-52 on tables partitioned by toYYYYMM(date). #99542 (Takumi Hara).
• Fix exception in functions operating on ColumnReplicated with unreferenced rows produced by JOIN. #99564 (Hechem Selmi).
• Fix CLEAR COLUMN not rebuilding projections and not reevaluation materialized columns that depend on the cleared column, which could cause exceptions or data corruption during subsequent merges. #99565 (Desel72).
• Fixed an exception (Bad get: has Tuple, actual type String) in ConditionSelectivityEstimator when a query uses IN with a single scalar query parameter (e.g. WHERE col IN ({p:String})) on a table that has column statistics and use_statistics is enabled. #99614 (Ilya Yatsishin).
• Part with unknown projections should not be marked as lost forever. #99623 (Sema Checherinda).
• Fix a rare logical error exception during vertical merge when SYSTEM STOP MERGES and SYSTEM START MERGES are executed concurrently. #99628 (Desel72).
• Fix dangling reference in injectRequiredColumns causing crash during merge. #99679 (Tuan Pham Anh).
• Fix undefined behavior in Avro format reader when reading numeric values that overflow the target column type. Now queries fail on overflows instead of silently producing incorrect values. #99697 (asyablue22).
• Fix parsing of shell-style quotes in arguments for the executable table function. #99794 (Nikita Semenov).
• Fix false-positive abort in NativeReader when deserializing a Native format stream with a row-count mismatch: changed from LOGICAL_ERROR to INCORRECT_DATA so the error is handled as a data error rather than triggering abort() in sanitizer/debug builds. #99822 (Rahul Nair).
• Fix process abort in Tuple column deserialization when the serialization kind in the binary stream is DETACHED. #99823 (Rahul Nair).
• Fix false LOGICAL_ERROR exception during filesystem cache dynamic resize due to a race condition in SLRU sub-queue promotion. #99850 (Alexey Milovidov).
• Fix async insert queries reporting zero written_rows, read_rows, and result_rows in query_log and client output. #99879 (Sema Checherinda).
• Fix exception "Bad cast from type X to Y" in KILL QUERY when the internal query against system tables returns columns wrapped in ColumnConst. #99881 (Alexey Milovidov).
• Fix logical error with correlated subquery within untuple argument. #99917 (Vladimir Cherkasov).
• Fixes an exception when calling right, rightUTF8, or other substring functions with a length of INT64_MIN (-9223372036854775808), which previously caused undefined behavior due to integer overflow. The functions now correctly report an ARGUMENT_OUT_OF_BOUND error. #99934 (Jimmy Aguilar Mena).
• Now ClickHouse should properly handle spark-style tables (where we have full absolute path for each file or relative path to common table path). Fixes #92348. #99935 (alesapin).
• Fix "Inconsistent AST formatting" exception for ALTER TABLE ... MODIFY QUERY with nested subqueries containing SETTINGS when the ALTER itself also has SETTINGS. #99938 (Nikita Mikhaylov).
• Revert #97114 "Move join step row estimation before check for 1 child" due to suspected performance regression. #99957 (Alexander Gololobov).
• Fixes a bug where ClickHouse could skip files if the Content-Length header was missing in their HEAD request response (for example, because of decompressive transcoding in GCS). #99971 (Yarik Briukhovetskyi).
• Fix assertion failure (exception in debug builds, incorrect results in release builds) when multiplying NumericIndexedVector aggregate states by an even integer constant, caused by self-XOR on aliased Roaring bitmaps in pointwiseAddInplace. #99976 (Desel72).
• Prevent Unexpected return type exception in legacy filter pushdown through chained JOIN USING when key types change after join conversions. #99999 (Alexey Milovidov).
• Fix LOGICAL_ERROR exception "Unexpected node type for table expression ... Actual IDENTIFIER" when a scalar subquery is used inside an unresolved table function argument, e.g. SELECT * FROM remote('localhost', view(SELECT 2 AS x), concat(x, (SELECT 1))). #100014 (Alexey Milovidov).
• Fixed INSERT with VALUES failing when the data was followed by a trailing SQL comment (-- or /* */) on the next line. The comment is now skipped instead of being parsed as another row. #100016 (Pratima Patel).
• Fix exception in arrayRemove when comparing tuples with NULL components. #100017 (Alexey Milovidov).
• Fix cross-user data leak in system.asynchronous_inserts: any user with SELECT on the table could see pending async insert entries belonging to other users. Entries are now filtered by the current user, unless the user has the SHOW_USERS privilege. #100024 (Shaohua Wang).
• Fixes case where Time64 to UInt64 cast could clamp values to 24 hours. #100025 (Yarik Briukhovetskyi).
• Fix local server crash when CREATE DICTIONARY has a definition with list value containing non-existing function. #100036 (Yakov Olkhovskiy).
• Fix CSV, MsgPack format not being able to parse Nullable(Tuple) properly. Closes #99753. #100038 (Nihal Z. Miaji).
• Fix CREATE VIEW failing with UNKNOWN_IDENTIFIER when using a WITH function-expression alias (e.g. tuple(...)) as the right-hand side of IN. #100042 (Peng).
• Fix timeseries aggregate functions (e.g. timeSeriesResampleToGridWithStaleness) failing with ILLEGAL_TYPE_OF_ARGUMENT when used with initializeAggregation or AggregatingMergeTree under parallel replicas. #100053 (Alexey Milovidov).
• Make correctly processing negative values inside NumericIndexedVectorDataBSI. #100086 (Daniil Ivanik).
• Fix accurateCastOrDefault and to*OrDefault functions not preserving Const column type for constant inputs. #100132 (Alexey Milovidov).
• Omitted query parameters with LowCardinality(Nullable(T)) type now correctly default to NULL, same as Nullable(T). #100144 (Denys Melnyk).
• Fix use-of-uninitialized-value in StringSearcher.h. #100225 (Konstantin Bogdanov).
• Allow cancellation of scalar subqueries and other analysis-time pipelines via Ctrl+C. Previously, pressing Ctrl+C during a long-running scalar subquery had no effect until the subquery completed. Also fix the progress bar and JSON statistics to correctly report rows read during scalar subquery execution, both in clickhouse-client and clickhouse-local. Co-authored with @YjyJeff. #100230 (Raúl Marín).
• Fixed a LOGICAL_ERROR exception in queries involving Dynamic columns with cross joins and runtime filters, caused by ColumnVariant::filter sharing variant column pointers instead of cloning them in the hasOnlyNulls optimization path. Closes https://github.com/ClickHouse/ClickHouse/pull/100147. #100234 (Pavel Kruglov).
• Fixed array of variant bug which may reinterpret data type upon calling arrayFirst/arrayLast function. For example, previously Array(Variant(Date, Bool)) is converted to Bool when the actual underlying variant type is Date. #100255 (timothygk).
• A few minor changes to functions: h3 functions now validate boundaries better; readWKB checks the size limits (a new setting, max_wkb_geometry_elements); random generator functions limit the maximum iterations in their computations. A follow-up for #93543. #100270 (Alexey Milovidov).
• Fixed an issue where cutURLParameter could incorrectly skip parameters when they appeared as substrings of other parameters. #100280 (Nikita Semenov).
• Fix exception when Iceberg metadata file path setting contains a null byte. #100283 (Alexey Milovidov).
• Fixed the quadratic number of run queries when distributed_index_analysis is used with predicates containing IN subqueries. #100287 (Anton Popov).
• Fix "Block structure mismatch" exception when using GROUP BY ... WITH TOTALS HAVING combined with UNION DISTINCT and nullable expressions. #100293 (Alexey Milovidov).
• Fix LOGICAL_ERROR exception in estimateCompressionRatio when block_size_bytes parameter is extremely large. #100298 (Alexey Milovidov).
• Fix "Inconsistent AST formatting" exception in debug builds when using GROUP BY CUBE(...) WITH ROLLUP or similar combinations. #100376 (Alexey Milovidov).
• Fix exception when creating a view with column aliases and SELECT * or EXCEPT/INTERSECT queries. #100386 (Alexey Milovidov).
• Fix DROP TABLE hanging indefinitely on Kafka engine tables when consumers are stuck in a rebalance after a heartbeat error. #100388 (Alexey Milovidov).
• Fix ReadBuffer is canceled. Can't read from it. exception in backup/restore operations using zip archives. #100400 (Alexey Milovidov).
• Fix TOO_MANY_ROWS exception for SELECT count() queries with max_rows_to_read / force_primary_key when data is split across multiple parts with non-aligned granule boundaries. #100408 (Alexey Milovidov).
• Fix system.completions to correctly filter databases, tables, and columns by access rights in all grant combinations: per-table, per-db, and per-column revoke. #100432 (Shaohua Wang).
• Fix SEGFAULT in NuRaft due to race condition. #100444 (Pablo Marcos).
• min/max/argMin/argMax now treat NaN consistently with ORDER BY: NaN is always skipped (returned only when all values are NaN). Previously, results depended on NaN position in the data due to IEEE 754 unordered comparison semantics. #100448 (Raúl Marín).
• Fixed a copy-paste bug where delta_lake_snapshot_end_version set without delta_lake_snapshot_start_version was silently ignored instead of producing a BAD_ARGUMENTS error. #100454 (Mohammad Lareb Zafar).
• StorageRabbitMQ::shutdown is not idempotent (it unconditionally accesses weak pointers and then destroys the corresponding shared pointers), but is now called twice: once in StreamingStorageRegistry and then in DatabaseCatalog. This fix makes the method idempotent and adds defensive null checks. #100455 (Miсhael Stetsyuk).
• Fix LOGICAL_ERROR exception when using accurateCastOrNull with QBit target type. #100470 (Raufs Dunamalijevs).
• Fix LOGICAL_ERROR exception "Stream ... not found" when inserting into a table with nested Array(JSON) columns in wide parts with optimize_on_insert=0. #100475 (Pavel Kruglov).
• Validate file entry paths in backup metadata to reject path traversal, absolute paths, and empty names during RESTORE. #100483 (Pablo Marcos).
• Fix LIMIT m OFFSET n WITH TIES syntax not working. This syntax is equivalent to LIMIT n, m WITH TIES which already worked. #100491 (Nihal Z. Miaji).
• Fix exception "No set is registered for key" when using IN with Nullable(Tuple) columns that have named fields and LowCardinality elements. #100523 (Alexey Milovidov).
• Fix heap-buffer-overflow in usearch sorted_buffer_gt::insert() that could crash or silently corrupt memory during vector similarity search. #100537 (Dustin Healy).
• Fix EXECUTE AS ignoring FORMAT and INTO OUTFILE clauses specified in the query. #100538 (pufit).
• Fix inconsistent AST formatting for SAMPLE with query-level OFFSET. Closes #100576. #100579 (Pavel Kruglov).
• Fix polaris catalog with azure. Since 25.12 this catalog with azure started to add bucket at the beginning of the path. For example abfss://polaris-polaris@<some_url>.windows.net/polaris-polaris/<other-path> instead of abfss://polaris-polaris@<some_url>.windows.net/<other-path>. This PR cuts bucket in the path. #100583 (Konstantin Vedernikov).
• Fix type mismatch exception in transform when default column is const on some blocks. Closes #100574. #100616 (Pavel Kruglov).
• Fixes NOT_FOUND_COLUMN_IN_BLOCK cases where the projection SELECT part has columns that do not exist in the original SELECT part of the query. Closes #100194. #100623 (Yarik Briukhovetskyi).
• Validate Npy format shape dimensions against file size and overflow limits to prevent denial of service from crafted .npy files with unreasonably large dimensions. Also reject empty shapes and cap per-row memory to 2 GiB. #100625 (Raúl Marín).
• Fix session_timezone being ignored when parsing DateTime values during async inserts (TCP) and all inserts over HTTP. #100647 (Sema Checherinda).
• Allow passing sharding key to cluster() and clusterAllReplicas() table functions when using a table function as the source (e.g. cluster('name', view(...), sharding_key)). #100665 (Sergey Veletskiy).
• Fix server crash (assertion failure) when using parametric aggregate functions with Array combinator and NULL arguments, such as quantileIfArrayArray(0.5)([[NULL]], [[1]]). #100679 (nerve-bot).
• Fix exception when computing common supertype for empty and non-empty tuples with use_variant_as_common_type enabled. #100699 (Antonio Andelic).
• Server no longer fails to start when an Azure blob storage disk is configured but the endpoint is temporarily unreachable (e.g. DNS failure). #100701 (Raúl Marín).
• Fix undefined behavior in positiveModulo when the unsigned divisor does not fit in the signed result type. #100705 (Raúl Marín).
• Fix server crash (logical error "Unexpected return type from __topKFilter") when use_top_k_dynamic_filtering is enabled and the ORDER BY column has Dynamic or Variant type. #100742 (Groene AI).
• Fix server crash when using has() function with PREWHERE/WHERE on a Tuple key containing LowCardinality elements. #100760 (Groene AI).
• Fix file_offset_of_buffer_end <= getFileSize() assertion failure (exception in debug builds) when reading from Log or StripeLog tables on S3 object storage with concurrent writes. #100763 (Alexey Milovidov).
• Fix an exception in the statistics selectivity estimator when a WHERE clause contains a function expression (e.g. toDecimal64(col, 3)) on a table with statistics enabled. The estimator now skips such predicates instead of attempting an invalid type cast. #100764 (Han Fei).
• Fixes a rare case where join with reordering can produce a wrong result. #100790 (Yarik Briukhovetskyi).
• Fix incorrect AggregateFunction argument types in optimized trivial count, which caused NUMBER_OF_ARGUMENTS_DOESNT_MATCH exception when querying expressions like count(v0 + v1) on distributed tables. #100794 (YjyJeff).
• Some catalogs can show some secrets in the SETTINGS section of select * from system.databases query result. This PR prevents such behavior. #100800 (Konstantin Vedernikov).
• Fix undefined behavior (signed integer overflow) in toStartOfInterval when using Week, Quarter, or Year intervals with an origin argument and extreme interval values. #100817 (Raúl Marín).
• Fix If, Distinct, DistinctIf, IfState aggregate function combinators with Tuple return type and one or more Nullable argument not being able to read older serialized states after introduction of Nullable(Tuple). Closes #98917. #100826 (Nihal Z. Miaji).
• Fix segfault in s3Cluster and distributed queries due to connection pool use-after-free. #100837 (Konstantin Bogdanov).
• Fix null pointer dereference segfault when loading dictionaries during server shutdown. Context::getUserDefinedSQLObjectsStorage (dereferences user_defined_sql_objects_storage) is called by dictionary threads concurrently with the main thread calling Context::shutdown (sets user_defined_sql_objects_storage to null). We need to make sure we disable future updates in the dictionaries loader, kill the currently running dictionary queries and join the dictionary loading threads - all before running Context::shutdown. Similar to what we do with normal queries. #100839 (Miсhael Stetsyuk).
• Fix buffer overflow in ULIDStringToDateTime when input contains non-ASCII bytes. #100843 (Konstantin Bogdanov).
• Fix crash (LOGICAL_ERROR) when querying a Merge table (or merge() table function) that wraps multiple tables including a Distributed table, with distributed_group_by_no_merge=1 enabled. #100859 (Groene AI).
• Cast_keep_nullable when enabled will not throw when casting dynamic null to variant. #100864 (Seva Potapov).
• Fix clickhouse-keeper-client get, exists, and ls commands printing duplicate watch_id error messages to stdout instead of stderr. #100893 (Mohammad Lareb Zafar).
• Fix exception in intDiv/intDivOrZero on arrays of nullable tuples, e.g. SELECT intDiv([divide((1, 2), ... AND NULL)], 2). #100895 (Raúl Marín).
• Evaluate engine arguments for StorageAlias before storing the definition, so that expressions like currentDatabase() are resolved to literals before being saved to the database. #100902 (Nikolay Degterinsky).
• Fix processAndOptimizeTextIndexFunctions when query_plan_merge_expressions = 0, where ExpressionStep is directly above ReadFromMergeTree. Fixes #100879. #100909 (Jimmy Aguilar Mena).
• Update replxx to include fix for out-of-bounds access in do_complete_line. #100925 (Azat Khuzhin).
• Fix wrong results when JOIN with shard-by-PK optimization uses query condition cache and some parts are filtered out by cached conditions. #100926 (Groene AI).
• Fix divide and intDiv returning ILLEGAL_DIVISION when used in filter expressions during index analysis in some cases. #100928 (Nihal Z. Miaji).
• Fixed "Target table doesn't exist" errors for materialized views with inner tables during async startup, caused by incorrect startup dependency ordering. #100946 (Nikolay Degterinsky).
• Fix undefined behavior (signed integer overflow) in parseDateTimeBestEffort when parsing datetime strings with more than 18 fractional-second digits. #100948 (Vasily Chekalkin).
• Fixed a crash when using a text search index with an IN clause containing a tuple subquery, e.g. WHERE (id, str) IN (SELECT (id, str) FROM ...), or when the number of columns in the subquery does not match the tuple on the left side of IN. #100959 (Anton Popov).
• Fixed crash when building a polygon dictionary from a MergeTree table that uses sparse columns serialization. #100964 (Anton Popov).
• Fix logical error "Invalid action query tree node" when using INTERSECT ALL / UNION ALL with constant-folded expressions. #100977 (Alexey Milovidov).
• Fix sumCountOrDefault aggregate function with one or more Nullable argument not being able to read older serialized states after introduction of Nullable(Tuple). Closes #100882. #101021 (Nihal Z. Miaji).
• Fix crash (Logical error: isConst/isSparse/isReplicated assertTypeEquality) in merge algorithms when lazy column replication (enable_lazy_columns_replication) produces ColumnReplicated columns that flow into merge-sort pipelines with late-arriving inputs. #101036 (Groene AI).
• Fix incorrect UNKNOWN_IDENTIFIER error when the same alias is used for multiple expressions in SELECT; the correct MULTIPLE_EXPRESSIONS_FOR_ALIAS error is now reported. #101040 (Alexey Milovidov).
• Fix ALIAS columns with DateTime/DateTime64 types not applying timezone conversion when the declared timezone differs from the expression timezone. #101043 (Alexey Milovidov).
• Fix row policies not being recorded in query_log for views, subqueries, and INSERT ... SELECT. Even though row policies were applied during query planning, they were not propagated from sub-planners to the parent planner for logging. Row policies (for logging only) are now kept in QueryAccessInfo so that both planners and sub-planners can populate them. #101044 (Narasimha Pakeer).
• Fix exception in DirectJoinMergeTreeEntity when pipeline blocks contain ColumnConst columns that are merged with regular columns. #101046 (Alexey Milovidov).
• Fix spurious space in CTE column alias formatting (WITH t (a, b) → WITH t(a, b)). #101049 (Alexey Milovidov).
• Fix remote/cluster table functions failing with nested table functions like merge when the analyzer is enabled. #101055 (Alexey Milovidov).
• Fix OFFSET being applied twice in distributed queries when prefer_localhost_replica=1, producing fewer rows than expected. #101071 (Nihal Z. Miaji).
• Fix crash when using the Regexp format with an invalid regular expression in format_regexp setting. #101074 (Nihal Z. Miaji).
• Fix "Illegal type Decimal64 of start parameter" error for timeseries aggregate functions when using serialize_query_plan=1 with parallel replicas. #101083 (Groene AI).
• Fix exception in optimizeLazyMaterialization when a projection with PREWHERE is used with ORDER BY ... LIMIT. #101115 (Anton Popov).
• Fix server crash (SIGABRT) when using aggregate functions with the internal-only Null combinator (e.g. sumNull, avgNull) and aggregate_functions_null_for_empty = 1 setting enabled. #101147 (Groene AI).
• Fix a use-after-free in the filesystem cache write path that could cause reads from freed memory when logging completed file segments (detected by MemorySanitizer in BuzzHouse). #101161 (Groene AI).
• Fix server crash with "Trying to attach external table to a ready set without explicit elements" when distributed index analysis encounters a GLOBAL IN predicate whose set was built without explicit elements. #101178 (Groene AI).
• Fix MAX/MIN aggregate functions on Decimal columns returning incorrect results when JIT compilation is enabled (after the compilation threshold is reached). #101203 (Raúl Marín).
• Fix minmax_count_projection and trivial COUNT(*) optimizations being permanently disabled after a lightweight delete, even after all parts with a mask of lightweight delete were merged away. #101212 (Anton Popov).
• Fix a case which can lead to Having zero bytes, ... logical error from cache arising from a remote object being overwritten in between list and read which previously resulted in a stale object metadata. #101219 (Kseniia Sumarokova).
• Fix server crash (LOGICAL_ERROR: Bad cast from ColumnVector to ColumnLowCardinality) when querying a MergeTree table with ORDER BY CAST(lc_column, 'Type') where lc_column has a LowCardinality type. #101220 (Groene AI).
• Fix cleanup of stale processing nodes in S3Queue. #101230 (Kseniia Sumarokova).
• Fix UB in mergeTreeAnalyzeIndexes() in case of invalid optimizations argument. #101253 (Azat Khuzhin).
• Fix Logical error: 'partitions_count > 0' exception when performing consecutive ALTER TABLE UPDATE on a partitioned Iceberg table. #101278 (Desel72).
• Fix wrong query results when a large integer constant (e.g. 256, 2147483648) is used as a boolean predicate in a WHERE clause with AND on MergeTree tables. For example, SELECT count() FROM t WHERE (2147483648 > b) AND 2147483648 would incorrectly return 0 instead of matching all rows. #101287 (Groene AI).
• Fix insert-select from delta lake cluster with replicated merge tree. #101299 (Konstantin Vedernikov).
• Fixed crash with "Logical error: Reading from materialized CTE before materialization" when a scalar subquery references a chain of dependent materialized CTEs. #101305 (Groene AI).
• Fix data race on storage_id in IStorage::getDependentViewsByColumn. #101385 (Nikolay Degterinsky).
• Fix BACKUP FROM SNAPSHOT AST formatting and cloning. #101405 (Pablo Marcos).
• Fix LOGICAL_ERROR crash "Current component is empty" when querying system.part_moves_between_shards with enforce_keeper_component_tracking enabled. #101462 (Groene AI).
• Fix segmentation fault in DataTypeDynamic::create() when the fuzzer generates a malformed Dynamic type AST. #101464 (Groene AI).
• Throw an error when delta_lake_snapshot_version or CDF version settings are used without DeltaKernel enabled, instead of silently returning wrong data. #101489 (Desel72).
• Fix NOT_FOUND_COLUMN_IN_BLOCK exception when using ARRAY JOIN with JOIN USING and analyzer_compatibility_join_using_top_level_identifier setting enabled. Close #101240. #101507 (Vladimir Cherkasov).
• Fix Iceberg INSERT retry loop failing when the table was created with iceberg_metadata_file_path and the target metadata version already exists. #101548 (Groene AI).
• Strip Nullable from result column in arrayIntersect and related functions to avoid serialization/deserialization mismatch. #101569 (George Larionov).
• Fix server crash (LOGICAL_ERROR) when SELECT-ing from a materialized view backed by an IcebergLocal table engine. #101577 (Groene AI).
• Fix incorrect error message when calling intExp10 with NaN argument — it said intExp2 instead of intExp10. #101582 (Krishna Chaitanya).
• Fix allow_statistics=0 not blocking ALTER TABLE ADD STATISTICS and ALTER TABLE DROP STATISTICS after refactoring in #100288. #101585 (Krishna Chaitanya).
• Fix KeeperMap CREATE TABLE failing with "Cannot create metadata for table" when leftover ZooKeeper nodes from a pre-25.1 partial drop are missing the drop_lock_version node. #101623 (Antonio Andelic).
• Fix possible logical error during reading Map subcolumns. Closes #100769. Closes #101336. #101641 (Pavel Kruglov).
• Fix exact subcolumn match priority over prefix match in getSubcolumnData to avoid possible crash. Closes #101271. #101645 (Pavel Kruglov).
• Fix crash (LOGICAL_ERROR: "ColumnUnique can't contain null values") when comparing a LowCardinality column with a Variant NULL constant while use_variant_default_implementation_for_comparisons is disabled. #101690 (Groene AI).
• What: Added empty-stream guard to Bzip2ReadBuffer so it returns EOF instead of throwing UNEXPECTED_END_OF_FILE when the inner stream is empty. #101691 (ClickGap AI Bot).
• What: Fixed the inverted description text for the alterable column in system.s3_queue_settings and system.azure_queue_settings — swapped 0 and 1 meanings to match the actual code behavior. #101703 (ClickGap AI Bot).
• Fix positiveModulo(tuple, number) incorrectly dispatching to division instead of modulo. #101709 (ClickGap AI Bot).
• Fixes a crash when thread_pool_size is configured on a cache-wrapped disk. Previously, FileCacheSettings::loadFromConfig() rejected thread_pool_size as an unknown setting, preventing the server from starting. The setting is a valid IDisk parameter that controls the number of threads used for disk-to-disk copy operations during background part moves. #101712 (Francisco).
• Fix RANGE_HASHED dictionary creation silently accepting a non-existent MAX range attribute and using the wrong type configuration when min and max range attributes had different types. The bug was a copy-paste error in buildRangeConfiguration that looked up min_attr_name instead of max_attr_name for the max attribute. #101732 (Yakov Olkhovskiy).
• Fix use-after-free crash in CPU lease scheduler when the wait timer outlives the worker thread whose ProfileEvents::Counters it references. #101761 (Antonio Andelic).
• Fixes bug in arrayLevenshteinDistanceWeighted and arraySimilarity functions. Closes #101725. #101767 (Mikhail f. Shiryaev).
• Fix Prometheus Query API ignoring POST form bodies. #101794 (James Cunningham).
• Fix exception escaping from S3 Client::~Client destructor causing server termination. #101798 (Gagan Dhakrey).
• Fix use-after-scope in parallel deserialization of Object type dynamic paths, which could cause crashes when reading tables with many dynamic paths. #101823 (Antonio Andelic).
• Fixed incorrect output in function formatDateTime with formatter%W with certain (non-default) formatting settings. #101847 (Robert Schulze).
• Fix shouldPatchFunction false negative in SYSTEM INSTRUMENT ADD when the search string first appears inside a template argument of the demangled symbol name. #101885 (Pablo Marcos).
• Fix UDF registry loss when ZooKeeper session expires during periodic refresh — all user-defined functions could become unavailable until a full refresh succeeds. #101891 (Nikita Fomichev).
• Fixed system.codecs description for AES_256_GCM_SIV to report AES-256 instead of AES-128. #101917 (Jimmy Aguilar Mena).
• Fix using wrong extremes in min-max index created on JSON column leading to wrong query result. Closes #101700. #101918 (Pavel Kruglov).
• The splitByString tokenizer now rejects empty separator strings. #101928 (Robert Schulze).
• Fix materialize_skip_indexes_on_merge=false not suppressing text (full-text) indexes during merge. Previously, only non-text skip indexes (minmax, set, bloom_filter) were suppressed; text indexes continued to be built, wasting CPU and I/O. #101932 (Groene AI).
• The sparseGrams tokenizer generated longer tokens than the provided max length (this was due to a hard-coded +2 in the implementation). #101934 (Elmi Ahmadov).
• Fix SIGSEGV in MergeTreeDataPartWriterWide::cancel when a stream constructor throws during addStreams, leaving a null entry in column_streams. #101936 (Antonio Andelic).
• Fixes an exception when querying Merge or Distributed tables with a full-text index and combined filter conditions that mix has*Tokens with LIKE, while query_plan_direct_read_from_text_index is enabled. #101939 (Jimmy Aguilar Mena).
• Fix undefined behaviour when parsing native protocol query packets with invalid QueryProcessingStage values. #101972 (Raúl Marín).
• Close TCP connection when an exception occurs during initial query parsing to prevent reading garbage from a desynchronized stream. #101989 (Raúl Marín).
• Fix SLRU race bug in filesystem cache 26.1+, which can lead to space reservation logical error. In debug build it can also lead to failed assert: 'Previous state is Evicting, but expected state to be Active while setting Evicting flag for 2c1e3484ecdc6b78a8978fa5b17c5097:0:339 (state: Evicting)'.. #101991 (Kseniia Sumarokova).
• Fix exception when casting a string with trailing data to empty Tuple() type. #102011 (Alexey Milovidov).
• Fixes incorrect row ordering in queries that use ORDER BY with the grace_hash join algorithm. Affected queries could return results in the wrong order, producing silently incorrect output. #102036 (János Benjamin Antal).
• Fixes a LOGICAL ERROR (Unexpected size of index type) that could occur in RIGHT JOIN and FULL JOIN queries when the max_bytes_in_join setting was configured. #102042 (Jimmy Aguilar Mena).
• Fixes cases where Time with negative values was returning wrong result on comparison with DateTime. Closes #101670. #102056 (Yarik Briukhovetskyi).
• Fix crash in UDF refresh caused by ZooKeeperRetriesControl retrying on a stale (expired) ZooKeeper session without renewing it. #102059 (Nikita Fomichev).
• Fix missing spaces when formatting unlock snapshot. close https://github.com/clickhouse/clickhouse/issues/101723. #102063 (Han Fei).
• Fix crash (SIGSEGV) when querying a view with a WHERE clause and the inner query produces columns with different types than the view metadata (e.g. Nullable from LEFT JOIN with join_use_nulls). #102085 (Miсhael Stetsyuk).
• Fix VectorSimilarityIndexCache entries never being evicted after part removal due to mismatched cache keys. #102152 (Seva Potapov).
• NACK broken messages when using rabbitmq storage. #102157 (Seva Potapov).
• Fix logical error when parsing incorrect empty tuple string. #102289 (Nihal Z. Miaji).
• Fix incorrect aggregation results (duplicate rows) when using optimize_aggregation_in_order=1 with GROUP BY columns ordered differently from the table's sorting key. #102299 (Groene AI).
• Fix crash in IcebergLocal ALTER TABLE ... UPDATE when using Avro format, caused by LowCardinality/Nullable wrapper types not being unwrapped before serialization. #102337 (Desel72).
• Fixed a segmentation fault in mutations on materialized columns without an expression. Closes #102185. #102342 (zoomxi).
• Coalescing merge tree fix for array type. This closes #89509. #102384 (Konstantin Vedernikov).
• Fix segfault (or LOGICAL_ERROR in debug builds) when reading Parquet files with bloom filter push down enabled and WHERE clause equality/inequality conditions. The crash occurred due to an out-of-bounds memory access in the Parquet prefetcher's bloom filter data retrieval, and could also cause non-deterministic wrong query results. #102385 (Groene AI).
• Fix LOGICAL_ERROR abort during SLRU filesystem cache dynamic resize caused by shared eviction statistics across sub-queues and incorrect recovery path for failed candidates. #102396 (Antonio Andelic).
• Fix failure to initialize on a fresh replica Alias tables without a target table in the Database Replicated. Closes #101320. #102397 (Nikolay Degterinsky).
• Fix out-of-bounds read in string search functions (countSubstrings, position, etc.) when searching for a needle consisting entirely of null bytes. #102401 (Raúl Marín).
• Full text index settings (enable_full_text_index, allow_experimental_full_text_index, use_skip_indexes_on_data_read) are no longer disabled when the compatibility setting points to a version older than 26.1. Previously this could prevent SharedDatabaseCatalog from creating tables with text indexes. #102422 (Nikita Fomichev).
• Fix out of bounds read in printf with trailing %. #102472 (Raúl Marín).
• Fixes a chassert exception ReadBuffer is canceled in debug builds in AsynchronousMetrics, caused by rewind not resetting the buffer cancellation flag. #102524 (Yuri Fedoseev).
• Fixed hasToken / hasTokenOrNull with separator-only needles (e.g. '()', '!!!') on columns with a text index: previously the index silently skipped all granules instead of throwing BAD_ARGUMENTS (for hasToken) or returning NULL (for hasTokenOrNull). #102544 (Jimmy Aguilar Mena).
• Fix OOMs on huge multi requests in the keeper. For OpenTelemetry tracing, we unconditionally allocate >1 KiB for OpenTelemetry spans in ZooKeeperRequest objects - meaning, for really huge multi requests, we try to allocate >10 GiB extra memory. To fix this, we now keep shared data in static memory and use std::unique_ptr over std::optional in ZooKeeperOpentelemetrySpans. #102586 (Miсhael Stetsyuk).
• Fix NamedCollection CurrentMetric being inflated by CREATE NAMED COLLECTION IF NOT EXISTS on existing collections, and not being initialized for collections loaded from config or SQL storage at startup. Closes #102507. #102598 (Pablo Marcos).
• Fix exception in getStructureOfRemoteTable when local shard returns empty columns due to concurrent DDL. #102604 (Alexey Milovidov).
• Fix LOGICAL_ERROR exception when multiple concurrent CREATE TABLE IF NOT EXISTS queries target the same S3Queue table on a Shared database. #102610 (Nikita Taranov).
• Fix LOGICAL_ERROR crash "Unexpected number of rows in column subchunk" in native Parquet V3 reader when reading nullable columns with a WHERE filter. #102628 (Groene AI).
• Fix AzureWriteMicroseconds profile event description saying "read" instead of "write". #102639 (Miсhael Stetsyuk).
• Bug with row policy that gives 'Not found column in block' exception in some special cases. #102648 (Yarik Briukhovetskyi).
• Fixed a server exception in ClusterDiscovery when a static cluster (defined in config) temporarily had no live nodes. #102661 (Kseniia Sumarokova).
• Fix wrong date data type inference in case of overflow after timezone adjustment. Closes #102601. #102674 (Pavel Kruglov).
• Fix SYSTEM WAIT VIEW hanging forever when the refreshable materialized view is dropped while the wait is in progress. #102681 (Nikolay Degterinsky).
• Fix CASE with Dynamic expression returning ELSE for all rows. Closes #102511. #102684 (Pavel Kruglov).
• Fix flattened Dynamic type serialization with binary encoded data types. Closes #101911. #102692 (Pavel Kruglov).
• Fix format_schema_source='query' silently ignoring multi-row results. Closes #101905. #102698 (Pavel Kruglov).
• Report actual exit code via SSH client instead of mapping all errors to 1. Closes #101741. #102700 (Konstantin Bogdanov).
• Fix losing HTTP headers for dynamic/predefined query handlers. Closes #101846. #102706 (Konstantin Bogdanov).
• Apply Poisson sampling correction to collapsed jemalloc heap profiles to match jeprof output. Previously the collapsed format underestimated actual allocation sizes by not accounting for the sampling probability. #102759 (Antonio Andelic).
• Fix the crash in the function hasPhrase with a NULL argument. #102802 (Nikita Taranov).
• Fix server crash (SIGSEGV) when reading Avro files with recursive schemas containing cyclic symbolic type references. Now such schemas are detected and rejected with a clear error message instead of crashing. #102853 (Groene AI).
• Fix server crash (LOGICAL_ERROR assertion) when a function on a Variant column hits a memory limit or other non-type-conversion exception during result casting in FunctionVariantAdaptor. The exception is now propagated correctly instead of being misclassified as an internal error. #102855 (Groene AI).
• Fix server crash in debug/sanitizer builds when std::length_error is thrown during schema inference (e.g., from extreme input_format_msgpack_number_of_columns values or malformed input data). #102859 (Groene AI).
• Make null representation in serialization of replicated and sparse columns respect settings (e.g. format_tsv_null_representation). #102888 (Hechem Selmi).
• Backported in #103499: Fix S3 requests failing with ios_base::clear: unspecified iostream_category error instead of being retried, caused by Poco BufferedStreamBuf::flushBuffer not handling short writes from the socket layer. #102894 (Sema Checherinda).
• Fix minmax_count_projection and trivial COUNT(*) optimizations being permanently disabled after a lightweight delete, even after all parts with a mask of lightweight delete were merged away. #102900 (Anton Popov).
• Fix random crashes in jemalloc due to LTO. #102913 (Azat Khuzhin).
• Optimize row policy OR-chains to IN in the new analyzer. #102915 (Azat Khuzhin).
• Fix jemalloc metadata corruption caused by page cache freeing with wrong alignment that may lead to crashes. #102918 (Azat Khuzhin).
• Plain INSERTs without materialized views no longer request excessive ConcurrencyControl slots and threads (max_threads instead of max_insert_threads), preventing CC slot starvation and thread count blowup on clusters with high INSERT throughput. #102961 (Sema Checherinda).
• Reintroduce ArrowMemoryPool to allow throwing MEMORY_LIMIT_EXCEEDED to avoid kernel OOM. #102999 (Azat Khuzhin).
• Fix cast_string_to_date_time_mode being ignored for CAST to Nullable(DateTime). Closes #101840. #103035 (Pavel Kruglov).
• Added support for ALIAS columns in text index direct read optimization. #103037 (Anton Popov).
• Backported in #103454: Fix SELECT DISTINCT silently returning incomplete results when an aggregate projection matched the query and some parts of the table had no projection data (e.g. the projection was added on a table that already held data, and MATERIALIZE PROJECTION was not run). Closes #102951. #103052 (Nihal Z. Miaji).
• Fix wrong results returned by WHERE x AND toNullable(N) on MergeTree tables when N is an integer wider than UInt8 (e.g. 256, 65535, 2147483648, or any negative integer). The filter incorrectly discarded all rows because splitFilterNodeForAllowedInputs used a NULL zero when converting the Nullable remainder of a reduced AND to boolean, turning the comparison into NULL under three-valued logic. #103077 (Groene AI).
• Fixed incorrect argument type reported in error messages of string search functions (e.g. locate, position) when arguments are passed in swapped order (locate(needle, haystack) with function_locate_has_mysql_compatible_argument_order = 1). #103102 (Alex Kuleshov).
• Fix waitForPause hanging indefinitely when disableFailPoint is called with no thread paused at the failpoint. #103119 (Shaohua Wang).
• Cap pre-auth TCP Hello packet strings to 64 KB and add handshake_timeout_milliseconds server setting to limit total handshake time, preventing unauthenticated clients from consuming excessive memory or holding threads indefinitely. #103284 (Sema Checherinda).
• Fix Parquet ColumnIndex stats min_value > max_value for String columns. #103334 (Saurabh Kumar Ojha).
• Check for malformed flattened Dynamic data in Native format. #103392 (Pavel Kruglov).
• Populate _time column from url table function. #103437 (Nikita Taranov).
• Fix SVE detection using SVE instructions when unavailable. #103568 (Raúl Marín).

Build/Testing/Packaging Improvement

• Libstemmer (Snowball) dependency now uses newer version v3.0.1. #99256 (Jimmy Aguilar Mena).
• Randomize settings in datastore-test: use_skip_indexes_for_top_k, use_top_k_dynamic_filtering, query_plan_max_limit_for_top_k_optimization. #91782 (Nikita Fomichev).
• Implement a stress test for functions, checking the soundness of their various properties. #93543 (Michael Kolupaev).
• Provide own CMake configuration for llvm-project instead of importing upstream one. #97453 (Konstantin Bogdanov).
• Randomize more optimize_* settings in the test infrastructure to improve coverage of query optimization passes. #97547 (Alexey Milovidov).
• Use Rust toolchain nightly-2026-03-22. #98602 (Konstantin Bogdanov).
• Use wasmtime v42.0.1. #98603 (Konstantin Bogdanov).
• Use llvm-project 22.1.1. #98882 (Konstantin Bogdanov).
• Replace SANITIZE_COVERAGE (custom sanitizer callbacks, symbol-level granularity) with LLVM source-based coverage (WITH_COVERAGE, -fprofile-instr-generate -fcoverage-mapping) for the nightly per-test coverage pipeline. The server now reads its own coverage mapping from ELF sections at startup and collects (file, line_start, line_end) tuples per test via a new SYSTEM SET COVERAGE TEST 'name' command. Test selection in targeted CI checks uses line-range queries against a new checks_coverage_lines CIDB table and ranks candidate tests by how many changed diff lines they cover. #99513 (Nikita Fomichev).
• Fix llvm-libc link error with -O0 build. #100023 (Zheguang Zhao).
• Fixed two error messages on container startup in case the configuration did not contain the logger.log and logger.errorlog settings (e.g. when all log messages are supposed to go to STDOUT/STDERR). #100239 (Simon).
• Prefer ld64.lld over Apple's ld (cctools-port ld64) for macOS builds. This should significantly reduce Darwin link times, as cctools-port's ld64 is very slow with -ffunction-sections and -dead_strip. Falls back to ld if ld64.lld is not available. #100275 (Alexey Milovidov).
• Tests to ensure that directories do not register any secrets (REST + Glue). #100307 (Konstantin Vedernikov).
• Repeat recently modified tests with different randomized settings. #100385 (Alexey Milovidov).
• Track #embed file dependencies in CMake and enable ccache depend mode for correct rebuilds. #100411 (Alexey Milovidov).
• Add correctness tests for TPC-H queries. #100580 (Raufs Dunamalijevs).
• Use aws-sdk-cpp 1.11.771. #100582 (Konstantin Bogdanov).
• Allow performance test XMLs to reference external SQL query files and settings via file attribute. #100747 (Raufs Dunamalijevs).
• Fix compilation with -march=x86-64-v4 by adding missing TargetSpecific.h include in LowerUpperImpl.h. #100932 (Alexey Milovidov).
• Fix build on gentoo by adding --no-default-config to cxxflags. #100973 (Isak Ellmer).
• Added utils/auto-bisect/ — a shell-based bisection framework that downloads pre-built CI binaries and runs a user-supplied test script to find the first commit that introduced a regression, without requiring a local build. #100989 (Nikita Fomichev).
• Disable ThinLTO by default in CMake so that local developer builds no longer implicitly enable it. CI release builds are unaffected since they explicitly pass -DENABLE_THINLTO=1. #101041 (Alexey Milovidov).
• Add TPC-DS SF1 benchmark to performance tests. #101209 (Raufs Dunamalijevs).
• Added stateless tests for MergeTree lightweight deletes covering: has_lightweight_delete flag lifecycle, COUNT(*) correctness with optimize_trivial_count_query, MATERIALIZED/DEFAULT column integrity, ReplicatedMergeTree flag recovery, read_in_order with deleted rows, multiple delete/merge cycles, _row_exists column hiding, predicate variety, and ALTER DELETE RBAC enforcement. #101792 (Nikita Fomichev).
• Distroless Docker images are now published with ubuntu and alpine variants for tagged releases. #101941 (Rahul Nair).
• Stack traces now show clean bare relative paths (e.g. src/Common/Exception.cpp) instead of paths polluted with the build directory (e.g. ./ci/tmp/fast_build/./src/Common/Exception.cpp). #102000 (Raúl Marín).
• Add a CI style check that rejects files larger than 5 MB committed to the repository, with a whitelist for existing legitimate test data. Remove unused 14 MB zookeeper_log.parquet. #102080 (Raúl Marín).
• Remove ~400 unused #include directives from headers to reduce compilation times. #102585 (Raúl Marín).
• Use wasmtime v43.0.1. #102603 (Konstantin Bogdanov).
• Use openssl 3.5.6. #102606 (Konstantin Bogdanov).
• Use xz 5.8.3. #102607 (Konstantin Bogdanov).
• Upgrade distroless Docker image base from Debian 12 (glibc 2.36, OpenSSL 3.0) to Debian 13 (glibc 2.41, OpenSSL 3.5), reducing CVE surface to zero reachable vulnerabilities. #101678 (Rahul Nair).

ClickHouse release 26.3 LTS, 2026-03-26. Presentation, Video

Backward Incompatible Change

• Downgrading after upgrading may cause data loss. Propagate data types serialization versions to nested data types. For example, String serialization version with_size_stream previously was applied only on top-level String columns and Tuple elements. Now it's applied to any String type inside any nested type like Array/Map/Variant/JSON/etc. This behaviour is controlled by MergeTree setting propagate_types_serialization_versions_to_nested_types that is now enabled by default. After this change, newly created data parts cannot be read by older versions, but old parts can be read on new version with no problems. Upgrade is safe, but downgrade is not — if you need to roll back after upgrading to 26.3, data written by 26.3 in columns with nested types will be unreadable! See #101429 for details. #94859 (Pavel Kruglov).
• Remove the hypothesis skip index type. It was an obscure, experimental feature with limited practical use. Creating tables with INDEX ... TYPE hypothesis will now produce an error. #96874 (Alexey Milovidov).
• Remove the experimental detectProgrammingLanguage function. #99567 (Alexey Milovidov).
• Fix NOT operator precedence to match the SQL standard: NOT now binds looser than IS NULL, BETWEEN, LIKE, and arithmetic operators. For example, NOT (x) IS NULL is now parsed as NOT (x IS NULL) instead of (NOT x) IS NULL. This may change the result of queries that relied on the previous (non-standard) behavior. #97680 (Alexey Milovidov).
• Corrects the metadata of normal projections so that projections with multi-column sorting keys are properly recognized. Builds on top of #90429. #91352 (Amos Bird).
• Fixed skip index files not respecting replace_long_file_name_to_hash setting, causing "File name too long" errors and broken index reads for indices with long names. Skip index filenames are now hashed when they exceed max_file_name_length, similar to column files. This is backward compatible (new servers read old parts), but downgrading (or old servers during a rolling upgrade) may cause long-named indices to be ignored. #97128 (Raúl Marín).
• Turn on async insert by default. ClickHouse will be batching all small inserts by default now. This setting is set under compatibility. If you set compatibility=<version less than 26.2> then default value would be the previous one, false. You can turn off/on async inserts at several levels: in the config in users profiles, for the session, for the query, or for the MergeTree table. #97590 (Sema Checherinda).
• Change the default value of mysql_datatypes_support_level from empty to decimal,datetime64,date2Date32, enabling proper mapping of MySQL DATE to Date32, DECIMAL/NUMERIC to Decimal, and DATETIME/TIMESTAMP with precision to DateTime64 by default. Previously, MySQL DATE columns were mapped to Date which cannot represent dates before 1970-01-01, causing data corruption. #97716 (Alexey Milovidov).
• Accept array of part names instead of regexp for mergeTreeAnalyzeIndexes{,UUID} since regexp is slow (Experimental feature). #98474 (Azat Khuzhin).
• Change default stderr_reaction from throw to log_last for executable UDFs. UDFs that write warnings to stderr no longer fail when exit code is 0. Exit code exceptions now include stderr content. #99232 (Xu Jia).

New Feature

• Added bucketed serialization for Map columns in MergeTree (map_serialization_version = 'with_buckets'). Keys are split into hash-based buckets so that reading a single key (m['key']) only reads one bucket instead of the entire column, providing 2-49x speedup for single-key lookups depending on map size. The number of buckets and the bucketing strategy can be controlled by new MergeTree settings: map_serialization_version, max_buckets_in_map, map_buckets_strategy, map_buckets_coefficient, and map_buckets_min_avg_size. #99200 (Pavel Kruglov).
• Support materialized CTE. Allow evaluating CTEs only once during query execution and store their results in temporary tables. Closes #53449. #94849 (Dmitry Novik).
• Allow certain SQL-standard functions without parentheses for compatibility, such as NOW. Closes #52102. #95949 (Aly Kafoury).
• You can now use the natural sort key function as naturalSortKey(s). #90322 (Nazarii Piontko).
• You can now use native JSON/Object input for JSONExtract functions. Closes #88370. #96711 (Fisnik Kastrati).
• If a query parameter has Nullable type and is not specified, we will assume that its value is NULL. #93869 (Vikash Kumar).
• Support auxiliary ZooKeeper for Replicated database. #95590 (RinChanNOW).
• Support has function for JSON type to check path existence, similar to Map. #96927 (DQ).
• Added the mergeTreeTextIndex(database, table, index) table function, which allows reading data directly from a text index. This function can be used for introspection or for performing aggregations on top of text index data. #97003 (Anton Popov).
• Add table_readonly MergeTree setting to mark tables as read-only, preventing inserts and modifications. #97652 (Alexey Milovidov).
• Add new setting use_partition_pruning and alias use_partition_key. Set it to false to disable partition pruning based on the partition key. #97888 (Nihal Z. Miaji).
• Implements ALTER TABLE ... EXECUTE expire_snapshots('<timestamp>') for Iceberg tables. #97904 (murphy-4o). #99130
• Allow each type=http entry in <protocols> to specify a custom <handlers> key pointing to a separate <http_handlers_*> config section, enabling different HTTP routing rules per port. #98414 (Amos Bird).
• Add pretty=1 option to EXPLAIN for tree-style indented output and compact=1 to collapse Expression steps, making query plans more readable. #98500 (Kirill Kopnev).
• Add restore_access_entities_with_current_grants server setting. When enabled, restored users/roles from backups have their grants limited to what the restoring user is allowed to grant (same semantics as GRANT CURRENT GRANTS), instead of failing with ACCESS_DENIED. #98795 (pufit).
• Add caseFoldUTF8 and removeDiacriticsUTF8 functions for Unicode case folding and diacritical mark removal. #98973 (George Larionov).
• Add normalizeUTF8NFKCCasefold string function for NFKC_Casefold Unicode normalization, which combines NFKC normalization with case folding. #99276 (George Larionov).
• Add asciiCJK tokenizer for full-text indexes and the tokens function. It splits text using Unicode word boundary rules: ASCII words are formed with connector characters (underscore, colon, dot, single quote), while non-ASCII Unicode characters become single-character tokens. #99357 (Amos Bird).
• Added max_skip_unavailable_shards_num and max_skip_unavailable_shards_ratio settings to limit how many shards can be silently skipped when skip_unavailable_shards is enabled. If the number or ratio of unavailable shards exceeds the configured threshold, an exception is thrown instead of returning silently incomplete results. #99369 (Alexey Milovidov).
• Users can now use SOME keyword for subquery expressions. It behaves identically to ANY. #99842 (Artem Kytkin).
• Add output_format_trim_fixed_string setting to strip trailing null bytes from FixedString values in text output formats. #97558 (NeedmeFordev).
• Support parenthesized table join expressions in FROM clause, e.g. SELECT * FROM (t1 CROSS JOIN t2). #97650 (Alexey Milovidov).
• Implement function toDaysInMonth: it returns the number of days in the month of the specified date. #99227 (Vitaly Baranov).

Experimental Feature

• Add experimental support for WebAssembly-based user-defined functions (UDFs), allowing custom function logic to be implemented in WebAssembly and executed within ClickHouse. Special thanks to Alexey Smirnov for contributing the Wasmtime backend support. #88747 (Vladimir Cherkasov). Incremental improvements for WASM UDF support. #99373 (Vasily Chekalkin).
• Add support for external SQL dialects using polyglot library. #99496 (Alexey Milovidov).
• Add ALP floating-point compression codec (without ALP_rd fallback for non-compressible doubles). #91362 (Nazarii Piontko).
• Add experimental lazy type hints for JSON columns. When enabled via allow_experimental_json_lazy_type_hints, ALTER TABLE ... MODIFY COLUMN json JSON(path TypeName) that only adds or modifies type hints completes instantly as a metadata-only operation, without rewriting historical data. Type hints are applied at query time for old parts and materialized during INSERTs and background merges. #97412 (tanner-bruce).
• Enable parallel reads from YTsaurus table engine. #97343 (MikhailBurdukov).

Performance Improvement

• Improve the performance of data lakes. In previous versions, reading from object storage didn't resize the pipeline to the number of processing threads. This gives orders of magnitude improvements (~40x) on multi-core machines. #99548 (Alexey Milovidov).
• Now, the relationship between enable_parallel_replicas and automatic_parallel_replicas_mode is as follows. A query can use parallel replicas only if enable_parallel_replicas > 0. Additionally, if automatic_parallel_replicas_mode=1, the decision whether to use parallel replicas is made during planning based on the previously collected statistics. If automatic_parallel_replicas_mode=0, parallel replicas will be used for all supported queries regardless of any statistics. One notable exemption is distributed insert-select with parallel replicas: in this case, queries will always be executed as if automatic_parallel_replicas_mode=0. #97517 (Nikita Taranov).
• Allow partition pruning when the predicate contains any comparison operator (=, <, >, !=) and the partition key is wrapped in a deterministic function chain (e.g. PARTITION BY x and predicates like cityHash64(x) % 5 > 2, toYYYYMM(x) < 2026, toYYYYMM(x) = 2026, or toYYYYMM(x) != 2026 will all use the partition key for pruning). Closes #28800. #98432 (Nihal Z. Miaji).
• Allow read-in-order optimization and primary-key pruning when the CAST target type is Nullable and the conversion is monotonic; for example, with PRIMARY KEY x, ClickHouse can use read-in-order optimization for ORDER BY x::Nullable(UInt64) and can apply primary-key pruning for predicates such as WHERE x::Nullable(UInt64) > 500000. #98482 (Nihal Z. Miaji).
• Allow index pruning and filter pushdown when an integral column is compared with a float literal; for example, predicates like WHERE x < 10.5 can now use the primary key for pruning, and filters such as prime < 1e9 or number < 1e5 are now pushed down for the primes() and numbers() table functions instead of causing unbounded execution. Closes #85167. #98516 (Nihal Z. Miaji).
• Added a new SLRU cache for Parquet metadata to improve read performance by removing the need to re-download files just to read metadata. #98140 (Grant Holly).
• Support swapping sides of ANTI, SEMI and FULL joins based on optimizer statistics. #97498 (Hechem Selmi).
• Optimize granules skipping for pointInPolygon for large polygons and fix pointInPolygon index analysis throwing during primary key pruning. #91633 (Nihal Z. Miaji).
• Improve performance of levenshteinDistance function. #94543 (Joanna Hulboj).
• Optimize batch decimal type conversions by avoiding per-element function calls. #95923 (Konstantin Bogdanov).
• Iceberg tables now support asynchronous metadata prefetching via iceberg_metadata_async_prefetch_period_ms table setting, which periodically pre-populates the metadata cache. Additionally, the iceberg_metadata_staleness_ms query setting allows SELECT queries to use cached metadata if it is fresher than the specified staleness, eliminating calls to the Iceberg catalog during request processing. #96191 (Arsen Muk).
• S3Queue ordered mode uses S3 ListObjectsV2 StartAfter to avoid re-listing full prefix history, reducing ListObjects calls. #96370 (Venkata Vineel ).
• Lower memory usage for inserts deduplication. In general the original block is needed for deduplication, but for sync insert we could omit it and save the memory for good. #96661 (Sema Checherinda).
• Use an arch-specific value for cache line size instead of a hardcoded value of 64. #97357 (Nikita Taranov).
• Slightly optimized reading from the text index dictionary, improving the overall performance of text index analysis. #97519 (Anton Popov).
• Speed up LZ4 decompression of 16 byte blocks in ARM. #97774 (Raúl Marín).
• Refactor tokenization to a new high-performance interface, replacing the old iterator-style API to support SIMD and stateful tokenizers. Part of #90268. #97871 (Amos Bird).
• Improved performance of text index analysis for queries with combined conditions involving both indexed and non-indexed columns. Previously, early exit optimization during index analysis was incorrectly disabled in such cases. #98096 (Anton Popov).
• Improve the performance of queries with constant expressions that generate very long arrays or maps. #98287 (Alexey Milovidov).
• Fix key condition analysis for DateTime64 primary keys compared with integer constants, which previously resulted in no granule pruning. #98410 (Amos Bird).
• The setting optimize_syntax_fuse_functions is enabled by default. #98424 (Alexey Milovidov).
• Optimize avgWeighted aggregate function by using local accumulators instead of per-row store-forwarding through aggregate state, improving performance by up to 27% for Nullable inputs. #98793 (Antonio Andelic).
• Improves performance and reduces memory usage for parallel window functions in certain scenarios, and for arrayFold workloads with large arrays. This can also reduce page-fault pressure and improve stability under tight memory limits for affected queries. #98892 (filimonov).
• Improve performance of sorted merges. #99013 (Artem Zuikov).
• Optimize INTERSECT ALL and EXCEPT ALL. #99097 (Raufs Dunamalijevs).
• Support the read_in_order_use_virtual_row optimization for reverse-order reads. #99198 (Vladimir Cherkasov).
• Reduce cache contention in RIGHT and FULL JOINs by checking if JoinUsedFlags is set before writing. #99274 (Hechem Selmi).
• Optimize PrefetchingHelper::calcPrefetchLookAhead by replacing floating-point math with pure integer arithmetic, improving instruction cache layout and reducing cycle overhead during aggregation loops. #99327 (Riyane El Qoqui).
• Reduce memory consumption of Keeper by replacing absl::flat_hash_set with CompactChildrenSet for storing node children. The new container stores 0–1 children inline without heap allocation, which covers the majority of Keeper nodes. This reduces KeeperMemNode size from 144 to 128 bytes. #99860 (Antonio Andelic).
• Aggregate projections are now correctly supported in views. Fixes #32753. #88798 (Amos Bird).
• Support OUTER to INNER join conversion optimization with join_use_nulls. Closes #90978. #95968 (Vladimir Cherkasov).
• Improve subcolumns reading by correct sizes calculation before reading. It reduces memory usage and speeds up the subcolumns reading. #96251 (Pavel Kruglov).
• Make mark, uncompressed and page caches to use separate jemalloc arena to avoid memory fragmentation when short lived allocations, i.e., for queries and requests are mixed with longer lived allocations for caches. #96812 (Seva Potapov). #98812. #99021
• Tables with DELETE TTL rules can now use the vertical merge algorithm. #97332 (murphy-4o).
• Apply data skipping indexes during distributed index analysis. #97767 (Azat Khuzhin).
• Marks of secondary indexes are now prewarmed when the prewarm_mark_cache setting is enabled (loaded into the index mark cache during data part fetches and table startup). #97772 (Anton Popov).
• Reduced locking during access control. #97894 (Nikita Taranov).
• When apply_row_policy_after_final or apply_prewhere_after_final is enabled, compound AND conditions in row policies and PREWHERE are now decomposed to extract sorting-key atoms for primary key index analysis. Previously, if a deferred filter contained a mix of sorting-key and non-sorting-key predicates (e.g. x > 1 AND y != 'foo'), the entire expression was excluded from index analysis. Now sorting-key atoms (like x > 1) are extracted and used for granule pruning, even from nested AND expressions. #98513 (Yarik Briukhovetskyi).
• Reduce lock contention in MergeTreeBackgroundExecutor by making task resources release without acquiring the lock. Closes #93620. #98604 (Dmitry Novik).
• Fix excessive memory usage (~514 MiB) during format auto-detection when reading non-Arrow data (e.g. JSON from url or file without explicit format), caused by the ArrowStream reader misinterpreting the first bytes as a huge metadata length. #98893 (Konstantin Bogdanov).

Improvement

• Makes it possible to parse GeoParquet files that contain different Geo type in the same column. #97851 (Mark Needham).
• Introduce tokensForLikePattern SQL function that tokenizes LIKE patterns while respecting wildcard semantics: % and _ are treated as wildcards, escaped wildcards (\%, \_) are treated as literals, and tokens adjacent to unescaped wildcards are discarded. #97872 (Amos Bird).
• Add a {_schema_hash} placeholder for the S3 table engine that inserts a hash of the table's column definitions into the S3 path. #98265 (Miсhael Stetsyuk).
• SymbolIndex, addressToSymbol, system.symbols, and buildId now work on macOS by parsing Mach-O symbol tables. #99014 (Alexey Milovidov).
• The system.stack_trace table now works on macOS, allowing introspection of all server thread stack traces. #98982 (Alexey Milovidov).
• Add per-server LDAP config option <follow_referrals> (default false) to control whether the LDAP client follows referrals. Disabling referral chasing avoids timeouts and hangs when searching from an Active Directory domain-root base DN. Referral-related log messages are moved from warn to trace. #96765 (paf91).
• We now track any data skipping indices that were used during query execution in the query_log table in a new column named skip_indices. Fixes #78676. Original author @pheepa. #87862 (Grant Holly).
• ACCESS_DENIED hints no longer reveal column names unless the user can show all required columns; database/table names remain visible in the hint. #91067 (filimonov).
• Add a dedicated cleanup thread for MergeTree to prevent cleanup delays under heavy merge load. This resolves #86181. #91574 (Amos Bird).
• Reload cluster config if IPs of local server’s hostname changed, instead of IPs of any host. Fixes #81215, #70156 and #65268. #93726 (Zhigao Hong).
• Allow optimize_aggregators_of_group_by_keys to correctly optimize aggregate functions in GROUPING SETS queries. #93935 (Xiaozhe Yu).
• Keeper-bench: report errors in metrics and generate json metrics file for --input-request-log mode. #95748 (Mohammad Lareb Zafar).
• Add new clause ROLE to CREATE USER. #97074 (Vitaly Baranov).
• You can now set internal_replication settings for a cluster created by the Replicated database. #97228 (Pervakov Grigorii).
• New setting allow_nullable_tuple_in_extracted_subcolumns controls whether extracted Tuple(...) subcolumns from Tuple, Variant, Dynamic and JSON are returned as Nullable(Tuple(...)) (NULL for missing rows) or as Tuple(...) (default tuple values for missing rows). Disabled by default, this setting can only be changed by restarting the server. #97299 (Nihal Z. Miaji).
• Add information about deferred filters as a separate item to EXPLAIN query output (when using Row Policies/PREWHERE with FINAL). Related: #91065. #97374 (Yarik Briukhovetskyi).
• Enable type_json_allow_duplicated_key_with_literal_and_nested_object by default. It allows to avoid errors about duplicated keys during parsing of JSONs like {"a" : 42, "a" : {"b" : 42}} that can be formatted by ClickHouse from original JSON data {"a" : 42, "a.b" : 42}. #97423 (Pavel Kruglov).
• Keeper improvement: find_super_nodes is a very useful command for debugging unexpected growth in the node count in Keeper. Unfortunately, if there are multiple super nodes, it's almost impossible to find more than one, because the command gets stuck forever traversing the children of the first encountered super node. This PR forbids traversing the children of super nodes. #97819 (pufit).
• Initial completion support for clickhouse-keeper-client. #97828 (Konstantin Bogdanov).
• Flush async logging buffers in case of crash. #97836 (Azat Khuzhin).
• Enable the impersonate feature by default (see EXECUTE AS target_user). #97870 (Vitaly Baranov).
• Improve canceling queries with SQLite table engine by KILL QUERY and cancel query (Ctrl+C) in clickhouse-client. #97944 (Roman Vasin).
• Add server setting jemalloc_profiler_sampling_rate to control jemalloc's lg_prof_sample and expose it as jemalloc.prof.lg_sample asynchronous metric. #97945 (Antonio Andelic).
• Support weights in concurrent bounded queue implementation. #97962 (Daniil Ivanik).
• Add sslmode to the allowed keys for PostgreSQL dictionary sources. Previously, sslmode was not in the dictionary_allowed_keys allowlist in PostgreSQLDictionarySource.cpp, making it impossible to configure SSL mode for PostgreSQL dictionary connections. This prevented dictionaries from connecting to PostgreSQL servers that require SSL (e.g., AWS RDS, which enforces SSL by default), as the connection would fail TLS negotiation and the server would reject the unencrypted fallback. #98014 (mcalfin).
• Show a clear "no such file" error when passing a non-existent file path to clickhouse or clickhouse-local, instead of a confusing generic message. #98048 (Raúl Marín).
• Text indexes can now be built on top of Nullable([Fixed]String) and Array(Nullable([Fixed]String)) columns. #98118 (Jimmy Aguilar Mena).
• Avoid dropping named collections that are dependencies of dictionary sources. #98127 (Pablo Marcos).
• Enable grace_hash join algorithm for queries with totals. #98144 (János Benjamin Antal).
• Cancel background merges early in DROP DATABASE for ordinary shared merge tree. #98161 (Shaohua Wang).
• Improve canceling queries with MongoDB and MySQL by KILL QUERY and cancel query (Ctrl+C) in clickhouse-client. #98187 (Roman Vasin).
• Remove NetlinkMetricsProvider and use procfs exclusively for per-thread taskstats metric collection. Netlink-based collection is problematic in containerized environments and has worse tail latency under contention. #98229 (Amos Bird).
• Refactor Iceberg manifest file handling to fix issues with manifest file caching. #98231 (Daniil Ivanik).
• Now we take into account cases where the sorting key of the table can be an expression like toDate(time), and can make the decisions about not-deferring expressions like this if they are part of filters. #98237 (Yarik Briukhovetskyi).
• Add a new MaxAllocatedEphemeralLockSequentialNumber metric for the maximum sequential number allocated for ephemeral lock znodes in ZooKeeper. #98243 (Miсhael Stetsyuk).
• Update clickstack to version 2.20.0. #98252 (Aaron Knudtson).
• Added a new profile event KeeperRequestTotalWithSubrequests that counts each subrequest within a multi-request individually, providing better visibility into the actual Keeper workload. The existing KeeperRequestTotal event continues to count each multi-request as a single request. #98348 (Antonio Andelic).
• SYSTEM RELOAD DICTIONARIES now reloads dictionaries in topological order so that dictionaries sourcing from other dictionaries see fresh data after reload. #98356 (Alexey Milovidov).
• Restart the statistics cache after changing the MergeTree setting. #98520 (Han Fei).
• Only "alive" replicas (that are connectable) participate in distributed index analysis. #98521 (Azat Khuzhin).
• Add a setting access_control_improvements.disallow_config_defined_profiles_for_sql_defined_users (disabled/allowed by default) that disallows using config-defined settings profiles (except for the default profile) for SQL-defined users. #98662 (Alexander Tokmakov).
• Cap the number of nodes used in the automatic parallel replicas heuristic to the actual number of nodes in the cluster (instead of only the max_parallel_replicas setting). #98668 (Nikita Taranov).
• Implement hedged requests and asynchronous reading for distributed index analysis. #98724 (Azat Khuzhin).
• Deserialization of binary AggregateFunction states now requires consuming the full input. If extra redundant trailing bytes are present, ClickHouse throws an exception instead of accepting malformed state data. #98786 (Nihal Z. Miaji).
• Make TRUNCATE DATABASE respond to query cancellation. #98828 (Shaohua Wang).
• Improve keeper-bench with request pipelining, warmup period, per-operation stats, reproducible seeds, and better error handling. #98906 (Antonio Andelic).
• Support SAMPLE clause in distributed index analysis. #98931 (Azat Khuzhin).
• Show chart title in dashboard even when query returns empty result or encounters an error. #98975 (Yash ).
• Analyzer error messages no longer dump all columns of a table (which could produce 150KB+ exceptions). Column lists are now capped at 10 entries. #99002 (Yash ).
• Properly return column stats from sub-queries with joins so that parent query can use them for join reordering. #99096 (Alexander Gololobov).
• Mark ZooKeeper session as expired immediately when finalization starts, instead of waiting for the send thread to exit. This allows other threads to establish a new session without delay. #99102 (Raúl Marín).
• Use more math functions from LLVM-libc: exp, exp2, expm1, fabs, fabsl, floor, fmodl, log, log2, logf, pow, scalbn, scalbnl, copysignl, nan, nanf, nanl, and the explogxf shared constants. #99118 (Konstantin Bogdanov).
• Reduce memory usage and fix potential duplicate output in system.jemalloc_profile_text collapsed format. #99121 (Antonio Andelic).
• Add is_subrequest column to system.aggregated_zookeeper_log to separate standalone requests from sub-requests inside Multi/MultiRead requests. Previously, sub-requests were aggregated into the same buckets as standalone requests, and since each sub-operation was logged with the total multi-request duration, the average latency became misleading. Sub-requests now have zero latency. #99169 (Miсhael Stetsyuk).
• Allow ALTER TABLE MODIFY COLUMN x TTL ... command without specifying column type. #99208 (Nikolay Degterinsky).
• Skip stale Keeper requests for sessions that have already disconnected, avoiding unnecessary Raft round-trips. The number of tracked finished sessions is capped by the max_finished_sessions_cache_size coordination setting. #99246 (Antonio Andelic).
• Support text index built on mapValues(map) with IN operator. #99286 (Anton Popov).
• Shell-like completion support in clickhouse keeper-client (handle completions of arguments in quotes, i.e. 'foo ba', handle escaped arguments, i.e. foo\ ba, make ls print quoted nodes, if they have whitespaces). #99312 (Azat Khuzhin).
• Prevent Keeper mntr command from getting stuck because of lock contention. #99472 (Antonio Andelic).
• Reduce lock contention in Keeper dispatcher by invoking callbacks and dispatching read requests outside mutex scope, and add profiled lock guards for observability. #99751 (Antonio Andelic).
• Tolerate missing padding at the end of the last block of parquet files. #99857 (Seva Potapov).

Bug Fix (user-visible misbehavior in an official stable release)

• Fixes how an Alias table target is saved as a DDL dependency when not fully qualified: it's now saved with the Alias table database instead of the session database. #95175 (Enric Calabuig).
• Fix wrong result or exception during reading subcolumns of ALIAS columns. #95408 (Pavel Kruglov).
• Fix missing column when non-standard identifier alias in JOIN with old analyzer. Fixes #25594, #47288 and #53263. #95679 (Zhigao Hong).
• Fixes a crash in Kusto dialect functions bin(), bin_at(), extract(), and indexof() when empty arguments are provided. #95736 (NeedmeFordev).
• Forbids mounting local_object_storage (which is used by datalakes above local filesystem and maybe by LocalDisk) anywhere apart from user_files_path in clickhouse-client. #96201 (Daniil Ivanik).
• In DeltaLake table engine fix logical race on snapshot version change, remove redundant heavy snapshot reloads. #96226 (Kseniia Sumarokova).
• Fix logical error on attaching a part in MergeTree if there were several chained renames between detaching and attaching. #96351 (Alexey Milovidov).
• Fix a bug where explicit settings sent alongside compatibility in the same request could be silently ignored when their value matched the server default. #97078 (Raufs Dunamalijevs).
• Fix the client reporting NETWORK_ERROR instead of the actual parsing error (with the correct row number) when an INSERT with parallel parsing encounters invalid data. #97339 (Alexey Milovidov).
• Fix sumCount aggregate function not being able to read older serialized states after introduction of Nullable(Tuple). Closes #97370. #97502 (Nihal Z. Miaji).
• Fix exception in tuple comparison involving Nothing type elements (e.g., comparing with NULL tuple elements) when used with GROUPING SETS and ORDER BY. #97509 (Alexey Milovidov).
• Fix non-deterministic uncompressed_hash computation for Compact MergeTree parts when multiple compression codecs are used, which could cause incorrect deduplication behavior. #97522 (Alexey Milovidov).
• Fix logical error about missing stream during INSERT SELECT with JSON and buckets in shared data. Closes #97331. #97523 (Pavel Kruglov).
• Fix MEMORY_LIMIT_EXCEEDED exceptions being incorrectly reported as CORRUPTED_DATA during SummingMergeTree and CoalescingMergeTree merges. #97537 (János Benjamin Antal).
• Fix "Context has expired" exception for correlated subqueries containing table functions like url(). #97544 (Alexey Milovidov).
• Fix exceptions and incorrect behavior in optimize_syntax_fuse_functions with aggregate projections, Date types, and column name preservation. #97545 (Alexey Milovidov).
• Remove incorrect replaceRegexpOne to extract query rewrite that produced wrong results when the regexp didn't match; also fix exception when replaceRegexpOne is used with GROUP BY ... WITH CUBE and group_by_use_nulls=1. #97546 (Alexey Milovidov).
• Fix DROP DATABASE with database_atomic_wait_for_drop_and_detach_synchronously hanging indefinitely when the query is killed. #97586 (Alexey Milovidov).
• Fix KILL QUERY not being able to terminate queries stuck in WITH FILL generation, dictionary loading via dictGet, or ALTER DELETE with mutations_sync=1 on ReplicatedMergeTree. #97589 (Alexey Milovidov).
• The loop table function was calling inner_storage->read() directly, bypassing the interpreter layer where row policies, column-level grants, and other security checks are applied. This allowed a user restricted by row policies to read all rows via loop(table) even when a direct SELECT returned zero rows. #97682 (pufit).
• Fixes incorrect partition pruning in cases of using pre-epoch DateTime64 with toDate() function. #97746 (Yarik Briukhovetskyi).
• After this patch, hasPartitionId will return false if another partition with a higher partition ID exists in the data part set. #97748 (Mikhail Artemenko).
• Fix possible crashes during reading of empty granules in advanced shared data in JSON. Closes #97563. #97778 (Pavel Kruglov).
• Fix Cannot schedule a file LOGICAL_ERROR on INSERT into Distributed due to race between DROP and INSERT. #97822 (Azat Khuzhin).
• Fixed ClickHouse server crash/assert in call to mapContainsKey/mapContainsKeyLike with tokenbf_v1 skip index. #97826 (Shankar Iyer).
• Fix LOGICAL_ERROR exceptions caused by LowCardinality inside compound types (Variant, Dynamic, Tuple) in concatWithSeparator, format, IN subqueries, GLOBAL IN, and joins with runtime filters. #97831 (Raúl Marín).
• Fix LOGICAL_ERROR exception Chunk info was not set for chunk in MergingAggregatedTransform when using ARRAY JOIN with merge() table function over multiple Distributed tables combined with GROUP BY. #97838 (Raúl Marín).
• Fix server crash (std::terminate) caused by an uncaught exception in the HTTP connection pool destructor when the connection group hard limit is reached under high concurrency. The exception HTTP_CONNECTION_LIMIT_REACHED could escape ~PooledConnection when recycling a connection back to the pool, leading to SIGABRT. #97850 (Antonio Andelic).
• Fix incorrect result when grace_hash algorithm is used with non-equi joins and left block cannot be processed completely because of the size constraints on the join result. #97866 (János Benjamin Antal).
• Fix performance inefficiency in DeltaLake metadata scanning introduced in #96686. #97880 (Kseniia Sumarokova).
• Fix data race in ZooKeeper client between sendThread and receiveThread. #97887 (Pablo Marcos).
• Fixes a bug where it was not possible to use CTE with distributed insert selects. Continuation of https://github.com/ClickHouse/ClickHouse/pull/87789. Closes #95837. #97889 (Yarik Briukhovetskyi).
• Fix exception from CachedOnDiskReadBufferFromFile::readBigAt. Closes #97325. #97890 (Kseniia Sumarokova).
• Fix LOGICAL_ERROR exception in Alias engine with materialized columns due to column mismatch. Closes #97907. #97921 (Kai Zhu).
• Fix Keeper data loss after restart when using Azure Blob Storage with s3_plain metadata for log storage. #97987 (Antonio Andelic).
• Fix JIT miscompilation of sign function for integer types wider than Int8 — values outside the -128..127 range could produce incorrect sign. #98012 (Alexey Milovidov).
• Fixed DUPLICATE_COLUMN exception and silent NULLs when reading Delta Lake tables that use column mapping "name" mode with struct fields whose names contain dots (e.g. STRUCT<`a.foo`: STRING, `b.foo`: STRING>). #98013 (Caio Ishizaka Costa).
• Fix mutation after lightweight update and secondary indices. #98044 (Raúl Marín).
• Fix incorrect result of FINAL queries when mixing primary key and non primary key skip indexes. #98097 (Raúl Marín).
• Enforce READ ON FILE checks for scalar file() and DESCRIBE TABLE file(). #98115 (Nikolay Degterinsky).
• Fixes a crash where querying files with a glob pattern (e.g., file('dir/**', 'LineAsString')) would throw an unhandled filesystem exception (STD_EXCEPTION) if the directory contained a dangling symlink. Dangling symlinks are now silently skipped, and the query returns results from all valid files. #98143 (Mark Andreev).
• Fix segfault in query plan optimization when converting outer join to inner join with arrayJoin in filter expression. #98147 (Alexey Milovidov).
• Fix ProtobufList format not working with Kafka engine due to read state not being reset between messages. #98151 (Alexey Milovidov).
• Fix logical error with analyzer_compatibility_join_using_top_level_identifier and ARRAY JOIN, closes #98164. #98179 (Vladimir Cherkasov).
• Set Watch component for watch responses in aggregated_zookeeper_log instead of leaving it empty. #98202 (Antonio Andelic).
• If the partition key columns are not covered by the sorting key, then partition pruning could incorrectly skip partitions containing rows that should "win" during FINAL deduplication. #98242 (Yarik Briukhovetskyi).
• Fix logical error "Bad cast from type DB::ColumnConst to DB::ColumnArray" in kql_array_sort_asc/kql_array_sort_desc when called with constant array arguments. #98251 (Alexey Milovidov).
• Fix out-of-bounds access in ColumnConst::getExtremes that could cause a crash when extremes = 1 is enabled. #98263 (Alexey Milovidov).
• Fix potential deadlock when two concurrent MOVE PARTITION operations work with the same pair of tables in opposite directions. #98264 (Alexey Milovidov).
• HTTP server now returns an error message in the response body for 400 Bad Request responses caused by malformed headers, instead of an empty body. #98268 (Alexey Milovidov).
• Fix wrong results with distributed index analysis (experimental feature) and query condition cache. #98269 (Azat Khuzhin).
• Fixed LOGICAL_ERROR exception "Invalid binary search result in MergeTreeSetIndex" triggered by toDate conversion on key columns with data crossing the 65535 boundary. #98276 (Alexey Milovidov).
• Fix LOGICAL_ERROR exception when a RIGHT JOIN wrapped in a CROSS JOIN is swapped by the query_plan_join_swap_table optimization in the legacy join step code path. #98279 (Alexey Milovidov).
• Validate corrupted data during DDSketch deserialization to prevent segfaults, exceptions, infinite loops, and OOM when reading corrupted quantilesDD aggregate function states. #98284 (Alexey Milovidov).
• Fix LOGICAL_ERROR "Trying to execute PLACEHOLDER action" when correlated columns from outer queries are referenced inside lambda functions such as arrayMap. #98285 (Alexey Milovidov).
• Fix logical error exception in caseWithExpression when CASE expression involves materialize(NULL) or other Nullable(Nothing) arguments. #98290 (Alexey Milovidov).
• Fix bad cast exception when filtering _table virtual column in merge table function. #98291 (Alexey Milovidov).
• Fix sporadic deduplication failure where re-inserts were incorrectly deduplicated due to inconsistent cleanup ordering between blocks/ and deduplication_hashes/ ZooKeeper directories. #98293 (Alexey Milovidov).
• Fix exception when ORDER BY ... WITH FILL is used together with LIMIT BY. #98361 (Alexey Milovidov).
• Fix silent data corruption when inserting a Parquet/Arrow Date column into an Enum column — now properly rejects the incompatible type conversion instead of storing invalid enum values. #98364 (Alexey Milovidov).
• Fix exception when reading an Arrow file with Array column into a table with Nested column. #98365 (Alexey Milovidov).
• Fix MATERIALIZE INDEX and MATERIALIZE PROJECTION mutations getting stuck when the index or projection is dropped before the mutation finishes. #98369 (Alexey Milovidov).
• Fix exception when reading from Nullable(Tuple(...)) where a Tuple element name collides with the Nullable null subcolumn. #98372 (Alexey Milovidov).
• Fix exception "Column ... query tree node does not have valid source node" when joining a Merge table (wrapping a Distributed table) with another table. #98376 (Alexey Milovidov).
• Fix incorrect Parquet Bool to FixedString conversion in native V3 reader that produced raw bytes instead of string representation. #98378 (Alexey Milovidov).
• Fix tryGetColumnDescription to filter subcolumns by parent column kind, consistent with other column lookup methods. #98391 (Alexey Milovidov).
• Accept base64 credentials without padding in HTTP Basic Auth. Some HTTP clients omit trailing = padding in the Authorization: Basic header, which previously caused authentication failures. #98392 (Amos Bird).
• Fix incorrect partition pruning results after merging parts with Nullable partition key columns, caused by wrong min-max index bounds. #98405 (Amos Bird).
• Fix rare exception in the pipeline executor, that could manifest as a Received signal 6 (only in debug builds), when pipeline expansion races with query cancellation. #98428 (Alexey Milovidov).
• Fix exception "Column identifier is already registered" when count_distinct_optimization is used with a QUALIFY clause. #98433 (Alexey Milovidov).
• Fix exception "cannot be inside Nullable type" when using IN/NOT IN with LowCardinality column arguments (e.g. a NOT IN (b) where a is LowCardinality(String)). #98443 (Alexey Milovidov).
• Fix "Pipeline stuck" exception in full_sorting_merge joins caused by a deadlock in PingPongProcessor when the FilterBySetOnTheFly optimization created a circular dependency with MergeJoinTransform. #98454 (Alexey Milovidov).
• Fix LOGICAL_ERROR exception "Projection cannot increase the number of rows in a block" when merging parts with TTL that deletes all rows and an aggregate projection with a constant GROUP BY key. #98458 (Alexey Milovidov).
• Fix logical error exception when CROSS JOIN is used together with INNER JOIN USING. #98459 (Alexey Milovidov).
• Fix null pointer dereference in dictGetOrDefault when the key argument is Nullable. #98460 (Alexey Milovidov).
• Fix exception in DISTINCT queries when using aggregate projections and materialize causes LowCardinality type differences between the query and the projection. #98462 (Alexey Milovidov).
• Fix LOGICAL_ERROR exception when arrayJoin is used in a filter expression with OUTER JOIN and join_use_nulls enabled. #98464 (Alexey Milovidov).
• Fix logical error exception "Replica decided to read in WithOrder mode, not in ReverseOrder" when using parallel replicas with optimize_aggregation_in_order. #98467 (Alexey Milovidov).
• Fixed ClickHouse Keeper disconnecting Java ZooKeeper clients after addWatch request. The Java client expects a 4-byte ErrorResponse body in the addWatch response, but Keeper was sending an empty body, causing EOFException and session disconnect. This broke Apache Curator's CuratorCache and any Java application using persistent watches. Fixes #98079. #98499 (Antonio Andelic).
• Fix zk_followers and zk_synced_followers Keeper metrics not decreasing when a follower goes down. Add new zk_learners and zk_synced_non_voting_followers metrics to the mntr four-letter-word command. Fixes #54173. #98504 (Antonio Andelic).
• Fix a LOGICAL_ERROR exception in renameAndCommitEmptyParts that could occur when TRUNCATE TABLE runs concurrently with OPTIMIZE TABLE using MergeTree transactions. #98508 (Alexey Milovidov).
• Fixed Keeper's secure raft port ignoring cipherList and dhParamsFile from openSSL configuration, always using defaults instead of user-specified values. Close #51188. #98509 (Antonio Andelic).
• Fixed misleading Keeper log messages like "Receiving request for session X took 9963 ms" where the reported time was actually spent waiting idle in poll() between heartbeats, not performing the operation itself. Fixes #79026. #98510 (Antonio Andelic).
• Fix unexpected result with read_in_order_use_virtual_row and monotonic functions, close #97837. #98514 (Vladimir Cherkasov).
• Fix LOGICAL_ERROR: Not-ready Set is passed as the second argument for function 'in' when using PREWHERE with IN subquery on MergeTree tables. #98522 (Alexey Milovidov).
• Fix Keeper TCP connections preventing graceful server shutdown by not responding to shutdown signal. #98525 (Alexey Milovidov).
• Fix exception "Sorting column wasn't found in the ActionsDAG's outputs" when query_plan_convert_join_to_in is enabled with query_plan_merge_expressions = 0. #98526 (Alexey Milovidov).
• Fix MongoDB dictionary source failing with named collections. Closes #97840. #98528 (Pablo Marcos).
• Fixed LOGICAL_ERROR when Identifier is empty after parameter substitution. #98530 (Pervakov Grigorii).
• Fix pipeline deadlock when using sort_overflow_mode = 'break' together with window functions. #98543 (Alexey Milovidov).
• Fix column rollback in Buffer engine during handling an exception during appending a new block. Old logic could lead to corrupted in-memory state of columns. #98551 (Pavel Kruglov).
• Fixed exception Bad cast from type ColumnConst to ColumnDynamic in null-safe comparison (<=> / IS NOT DISTINCT FROM) with const Dynamic or Variant columns and NULL. Also fixed IS DISTINCT FROM with Dynamic/Variant vs NULL always incorrectly returning 0. #98553 (Alexey Milovidov).
• Fixed usage of the text index with other skip indexes. Previously, logical errors such as "Trying to get non-existing mark" could be thrown when a query filter utilized a text index and other regular skip indexes simultaneously. #98555 (Anton Popov).
• Fix logical error "TABLE_FUNCTION is not allowed in expression context" when a table function with an alias appears multiple times in the same query scope (e.g. in both PREWHERE and QUALIFY clauses). #98557 (Alexey Milovidov).
• Fix distributed index analysis with expressions (not just columns) in PK (leads to zero filtering of redundant granules on remote replicas). #98561 (Azat Khuzhin).
• Disallow dropping column when its subcolumns are used in other columns default/alias expressions and use analyzer for default expressions on alter drop column. #98569 (Nikita Mikhaylov).
• Fix S3 requests being incorrectly retried on non-retryable errors (including HTTP_CONNECTION_LIMIT_REACHED) in the HTTP client. #98598 (Sema Checherinda).
• Fixes a decimal overflow when partition pruning with DateTime64. #98628 (Yarik Briukhovetskyi).
• Fix two bugs in JIT expression compilation: a copy-paste error in nativeCast type checking that made integer-to-integer and float-to-float cast branches unreachable, and incorrect nullptr TargetMachine passed to LLVM PassBuilder preventing target-specific optimization passes from being registered. #98660 (Alexey Milovidov).
• Fix RBAC bypass that allowed users to DESCRIBE any table via remote(), remoteSecure(), cluster(), or clusterAllReplicas() pointed at localhost, without requiring SHOW_COLUMNS privilege. #98669 (pufit).
• Fix BAD_GET exception and incorrect query results when a non-boolean expression (e.g. sin(col)) is used in both WHERE and SELECT with a JOIN, due to filter push-down optimization corrupting shared DAG nodes. #98681 (Alexey Milovidov).
• Fix LOGICAL_ERROR "Replica decided to read in Default mode, not in WithOrder" when using read_in_order_through_join with parallel replicas. #98685 (Alexey Milovidov).
• Fix exception "Bad cast from type DB::TableFunctionNode to DB::QueryNode" when using input table function as an argument of remote. #98694 (Alexey Milovidov).
• Fix outdated data parts resurrection caused by incorrectly cleaning up empty covering parts. #98698 (Shaohua Wang).
• Fix exception in LogicalExpressionOptimizerPass when a boolean function in an equals comparison returns a Variant type. #98712 (Alexey Milovidov).
• Fix parseDateTimeBestEffort incorrectly parsing words starting with month/weekday prefixes. Closes #97965. #98742 (Pavel Kruglov).
• Fix UNKNOWN_IDENTIFIER exception when querying merge() table function or Merge engine over tables with JSON columns that have different parameters (e.g. different SKIP fields) and ALIAS columns referencing JSON sub-paths, with the new analyzer enabled. Closes #97812. #98753 (Pavel Kruglov).
• Fix optimize_skip_unused_shards optimization with the analyzer in case Distributed storage is used in a View. #98754 (Nikolai Kochetov).
• Fix tuple subcolumn access by name (e.g. SELECT x.a for Tuple(a UUID, b Int32)) for external tables passed via --external in clickhouse-client. Closes #96925. #98755 (Pavel Kruglov).
• Fix reverseUTF8 exception on invalid (truncated) UTF-8 input. #98770 (Alexey Milovidov).
• Fix detecting set skip index usefulness with OR with false (i.e. or(x, 0)) predicate. #98776 (Azat Khuzhin).
• Fix a LOGICAL_ERROR exception (Block structure mismatch in removeUnusedColumns) that could occur with FINAL + PREWHERE + constant WHERE expression + column-independent aggregates like count(). #98778 (Alexey Milovidov).
• Make system.trace_log entries for ClickHouse dictionaries' auto-reloads have non-empty query IDs. #98784 (Miсhael Stetsyuk).
• Fixes a crash where we could de-reference a null pointer in system tables created between the time when we snapshot the tables in the IDatabaseTablesIterator::table() call and the tables changing in another thread during later iteration. #98792 (Grant Holly).
• Fix SYSTEM START REPLICATED VIEW not waking up the refresh task. #98797 (Pablo Marcos).
• Fix exception "Inconsistent table names" when using view() table function containing JOINs inside another JOIN (only with old analyzer). #98809 (Alexey Milovidov).
• Fix adjusting RLIMIT_SIGPENDING (via pending_signals). #98829 (Azat Khuzhin).
• Fix exception when composing loop with cluster table functions. #98860 (Konstantin Bogdanov).
• LEFT ANTI JOIN with multiple join key columns returned wrong results when enable_join_runtime_filters=1 (which is default). #98871 (Alexander Gololobov).
• Fix WITH FILL STALENESS producing extra filled rows when data is read in multiple chunks (e.g., with small index_granularity). #98895 (Alexey Milovidov).
• Fix "RPNBuilderFunctionTreeNode has A arguments, attempted to get argument at index B" LOGICAL_ERROR. #98900 (Azat Khuzhin).
• Fix memory tracking drift caused by failed allocations not being rolled back, nallocx(0) undefined behavior, and off-by-one in global peak tracking. Extend tracking to cover io_uring ring buffers. #98915 (Antonio Andelic).
• Forbid attaching to local data lake tables outside user paths, not only creating them. #98936 (Daniil Ivanik).
• Fix a race condition that could cause a "ReadBuffer is canceled" exception in queries using urlCluster or similar cluster table functions. #98955 (Alexey Milovidov).
• Fix LOGICAL_ERROR exception in financial functions (financialNetPresentValue, financialInternalRateOfReturn, etc.) when BFloat16 type arguments are passed. #98958 (Alexey Milovidov).
• Fix skip indexes (and primary key conditions) not being applied for ALIAS columns when query plan expression merging is disabled (query_plan_merge_expressions = 0 or query_plan_enable_optimizations = 0). #98960 (Peng).
• Increment InsertQuery ProfileEvent for async inserts. Closes #98626. #98962 (Narasimha Pakeer).
• Fix exception "Inconsistent KeyCondition behavior" in debug builds when primary key contains NaN float values, by making accurateLess and accurateEquals handle NaN consistently with ClickHouse sort order. Closes #98075. #98964 (Alexey Milovidov).
• SummingMergeTree no longer sums Bool (and other domain type) columns. Bool values are kept as-is instead of being arithmetically summed. #98976 (Yash ).
• Fixes an exception Scalar doesn't exist that occurred when querying a remote shard with optimize_const_name_size set and enable_scalar_subquery_optimization = 0. Large constants replaced with __getScalar references in the remote query were not being sent to the shard, causing the query to fail. #98979 (andriibeee).
• Fix NOT_FOUND_COLUMN_IN_BLOCK for some queries with GROUP BY and expressions that include inverse dictionary lookup, Date/DateTime conversion comparisons, and tuple comparisons. Closes #98888. #98980 (Nihal Z. Miaji).
• Fixed undefined behavior (null pointer dereference) when altering a version/sign/is_deleted column to EPHEMERAL or ALIAS in MergeTree engines. Such alterations are now properly rejected. #98985 (Alexey Milovidov).
• Fixed an issue where system.grants omitted the regular expression parameters for URL and S3 grants in the access_object column. #98987 (DQ).
• Fixed Iceberg BigLake reads: ADC credentials are now forwarded to the GCS S3 client (fixing 403 errors), OAuth2 credentials are URL-encoded before sending (fixing auth failures for tokens with special characters), and namespace traversal no longer aborts on BigLake HTTP 400 responses. #98998 (Nikita Fomichev).
• Fixed clickhouse-client failing to switch timezone when TZ environment variable uses POSIX file path syntax (e.g. TZ=:/etc/localtime). #99000 (Yash ).
• Fix incorrect or less pruning when startsWith, LIKE, NOT LIKE used with FixedString column. Additionally, FixedString to String cast function can now prune granules when wrapped around key column. Closes #98940. #99001 (Nihal Z. Miaji).
• Fixed windowFunnel with strict_deduplication returning incorrect level when a duplicate event was encountered. #99003 (Yash ).
• Fixes a bug where EXISTS would ignore LIMIT and OFFSET clauses in subqueries, causing incorrect results when the subquery returned no rows due to an offset or a zero limit. Closes #88722. #99005 (andriibeee).
• Fix "Block structure mismatch" exception when filter push-down optimization encounters an AND expression that short-circuits to a constant with GROUPING SETS. #99010 (Alexey Milovidov).
• Fix exception when reading patch parts (lightweight updates) without _part_offset column in the query plan. #99023 (Alexey Milovidov).
• A query like SELECT * FROM table WHERE pk_id = '' where pk_id is the primary key and of String type will now correctly use the primary key index for filtering granules. #99027 (Shankar Iyer).
• Fix DEPENDENCIES_NOT_FOUND exception in Kafka engine when materialized view is detached while the background thread is streaming data. #99028 (Alexey Milovidov).
• Fix exception when creating a table with an EPHEMERAL column that has the same name as a virtual column (e.g., _part_offset). #99031 (Alexey Milovidov).
• Fix misleading "inflate failed: buffer error" when reading non-existent compressed files via url() table function with glob patterns. Now returns empty result as expected when http_skip_not_found_url_for_globs is enabled. #99034 (Alexey Milovidov).
• Fix server crash (std::terminate) when executing ALTER TABLE ... DROP PART on a patch part after a schema change (e.g. ADD COLUMN). The crash was caused by missing system columns (_part) in the empty coverage part metadata, leading to an uncaught exception inside a NOEXCEPT_SCOPE. #99036 (Peng).
• ClickHouse server process could crash if there was a memory limit exceeded exception thrown during a cached disk read. That is now fixed. #99042 (Shankar Iyer).
• Fix LOGICAL_ERROR when querying a table that has both a ROW POLICY and an ALIAS column using dictGet. The issue was caused by premature access to the table expression during ALIAS column resolution in the new analyzer. #99065 (Peng).
• Fix out of bounds error when user tries to query only virtual columns from Iceberg table with Avro format for data. It's super rare scenario so not marking it as critical. Fixes #88238. #99080 (alesapin).
• Fix segfault in recursive CTE with remote() + view(). #99081 (Konstantin Bogdanov).
• Skip unnecessary extra index analysis when read-in-order optimization is applied. #99084 (Vladimir Cherkasov).
• Fixed a crash triggered by a memory limit exception thrown during patch part application. #99086 (Anton Popov).
• Fix debug assertion in DDLWorker caused by stale first_failed_task_name after a ZooKeeper entry is deleted during reinitialization recovery. #99099 (Antonio Andelic).
• Fixed rebuild of text indexes on merges with TTL. #99107 (Anton Popov).
• Fix crash in ALTER TABLE ... REMOVE SETTINGS query for Iceberg table engine. Fixes #86330. #99108 (alesapin).
• Fixes a bug in query_plan_convert_any_join_to_semi_or_anti_join optimization, returning an incorrect result for unmatched rows. Related: https://github.com/ClickHouse/ClickHouse/pull/95995. #99112 (Yarik Briukhovetskyi).
• Fix LOGICAL_ERROR exception in ASTColumnsExceptTransformer::transform. #99119 (Pablo Marcos).
• Fix RBAC bypass that allowed users to obtain table structure via DESCRIBE TABLE or CREATE TABLE AS on table functions (mysql(), postgresql(), sqlite(), arrowFlight(), jdbc(), odbc(), etc.) without the required source access privileges. For functions that infer schema from remote servers, this also allowed triggering outbound connections (SSRF) without authorization. #99122 (pufit).
• Fix Keeper crash (segfault in NuRaft) during dynamic reconfiguration and leadership transfer. #99133 (JIaQi Tang).
• Fix crash on usage of Buffer table with SAMPLE when destination does not support it. #99141 (Kseniia Sumarokova).
• Fix LOGICAL_ERROR due to patch parts column order mismatch. #99164 (Pablo Marcos).
• Fix very rare crash when Iceberg table contains files of mixed format (ORC and Parquet). Fixes #88126. #99168 (alesapin).
• Fix max_execution_time not being applied for backup/restore. #99205 (Kseniia Sumarokova).
• Fix insert_deduplication_token being silently ignored for INSERT SELECT queries without ORDER BY ALL. Previously, deduplication was disabled entirely for unsorted INSERT SELECT, even when an explicit user token was provided. Now, providing insert_deduplication_token is sufficient to enable deduplication regardless of ORDER BY ALL. #99206 (Desel72).
• Fix excessive access checks during InverseDictionaryLookupPass optimization by checking CREATE_TEMPORARY_TABLE grant once before the pass instead of for every visited node. #99210 (Mikhail Artemenko).
• Fix clickhouse format --obfuscate producing invalid SQL by obfuscating skip index types, compression codec names, database engine names, and dictionary layout/source definitions. #99260 (Raúl Marín).
• Fixed a bug where, in some cases, comparing between Time[64] and DateTime[64] types was confusing; now, in cases like this, Time[64] values are promoted to DateTime[64] by adding the 1970-01-01 as a date part. #99267 (Yarik Briukhovetskyi).
• Clamp settings constraints in DDL worker for distributed DDL queries. #99317 (Pablo Marcos).
• Fix minor issues with TOTP authentication: the --one-time-password CLI option with empty password, validation of <digits> and <period> configuration values. #99322 (Vladimir Cherkasov).
• Fix logical error unordered_map::at: key not found in Avro output format when serializing Enum8/Enum16 columns with values not present in the enum definition. #99332 (Desel72).
• Fix CHECK TABLE with sparse serialization inside Tuple with Dynamic. Closes #96588. #99351 (Pavel Kruglov).
• Fixed too strict validation of text index preprocessor. #99359 (Anton Popov).
• Fix compatibility when upgrading replicated tables with implicit minmax indices from 25.10 to newer versions. #99392 (Raúl Marín).
• Removed support for negated functions (notEquals, notLike, notIn) in text index analysis. These functions could never skip any granules, so analyzing the index for them only added overhead without any benefit. #99393 (Anton Popov).
• Fix optimize_skip_unused_shards with a new analyzer for the case when a Distributed table was used inside an IN subquery. #99436 (Nikolai Kochetov).
• Fix heap-use-after-free in INTERSECT/EXCEPT when the query produces duplicate column names. #99471 (Alexey Milovidov).
• Fix logical error in ALTER TABLE ... DROP PART when a typed query parameter is used for the part name. #99489 (Alexey Milovidov).
• Fixed NOT_FOUND_COLUMN_IN_BLOCK exception when a text index predicate (e.g. hasAllTokens) is referenced in both SELECT and WHERE clauses via an alias. #99504 (Anton Popov).
• Fix incorrect results when using hasAllTokens with OR across columns that have separate text indexes. #99505 (Anton Popov).
• Initialize page cache in clickhouse-local so that page_cache_max_size setting takes effect. #99510 (Alexey Milovidov).
• Fixed rare incorrect marking of a data part as broken and detaching it after DETACH/ATTACH TABLE query. #99529 (Anton Popov).
• Fix std::length_error exception when querying empty system tables with Pretty format via HTTP interface. #99541 (Alexey Milovidov).
• Fix LOGICAL_ERROR when using ALTER TABLE ADD COLUMN to create an EPHEMERAL column with the same name as a virtual column (e.g. _part_offset). #99549 (Alexey Milovidov).
• Fix VectorSimilarityIndexCache entries never being evicted after part removal due to mismatched cache keys. #99575 (Seva Potapov).
• Forbid reading Google credentials from a local file. This setting is insecure because it allows reading other credentials if the file path is known. #99584 (Konstantin Vedernikov).
• Fix performance degradation in the analyzer. Prune unused columns from ARRAY JOIN. #99587 (Dmitry Novik).
• Fixed reading of text index in table with existing lightweight deletes and row policies. #99661 (Anton Popov).
• Fix nullptr dereference in Parquet reader when filter-in-decoder path encounters filtered-out pages. Closes #99676. #99677 (Alexey Milovidov).
• Fix incorrect seek in AsynchronousReadBufferFromFileDescriptor with O_DIRECT. Closes #99358. #99678 (Pavel Kruglov).
• Fixed heap-buffer-overflow in CompressionCodecT64 and process abort in CompressionCodecMultiple when decompressing malformed compressed data. Both issues were found by new libFuzzer targets. The codecs now throw an exception instead of crashing. #99680 (Rahul).
• Delay processing until server has finished loading all the tables. #99700 (Seva Potapov).
• Fix MySQL dictionary source bypassing RemoteHostFilter for inline DDL params. #99720 (Shaohua Wang).
• Fix logical error when iterating over data lake tables in system.tables. #99739 (Konstantin Vedernikov).
• Fixed analysis of predicates with the IN function by text index with the preprocessor. Fixed the collision of searched tokens in the text index, which could lead to incorrect results. #99755 (Anton Popov).
• Fix infinite loop when reading Npy format files with negative shape dimensions. #99812 (Desel72).
• Fix global-buffer-overflow in CRC32 function on FixedString arguments when evaluated with zero rows during query plan header computation. #99835 (Alexey Milovidov).
• Fix crash (null pointer dereference) when executing ALTER TABLE ... MODIFY COLUMN ... COMMENT on Iceberg tables. #99838 (Desel72).
• Fix aggregate_functions_null_for_empty setting to work with aggregate functions returning non-Nullable types such as Array or Map (e.g., groupArray, sumMap). #99839 (Alexey Milovidov).
• Fix LOGICAL_ERROR exception in midpoint function when called with mixed signed/unsigned integer types. #99867 (Alexey Milovidov).
• Fix "Block structure mismatch" exception in queries with HAVING clause where the filter expression contains both an aggregate wrapped in a NULL-producing function and materialize(0). #99915 (Alexey Milovidov).
• Fix assertion failure in sipHash128Keyed (and similar keyed hash functions) when the data argument is a Map with array keys or other nested array types. #99921 (Alexey Milovidov).
• Fix LOGICAL_ERROR exception "Not-ready Set" in IN function during query plan optimization with convertAnyJoinToSemiOrAntiJoin. #99939 (Alexey Milovidov).

Build/Testing/Packaging Improvement

• Reduce compilation time by removing heavy header includes and moving expensive template instantiations out of headers. #97893 (Raúl Marín).
• Reduce compile time of arithmetic functions and related headers by shrinking template dispatch matrices and removing heavy includes. #98204 (Raúl Marín).
• Use mongo-c-driver 2.2.2. #98304 (Konstantin Bogdanov).
• Use postgres REL_18_3. #98306 (Konstantin Bogdanov).
• Enable jemalloc allocator for UBSan builds to avoid RSS accumulation from glibc malloc's poor memory reclamation behavior. #98444 (Alexey Milovidov).
• Use Rust v0 symbol mangling and strip internal symbols from PRQL library to reduce symbol name bloat from parser combinator libraries. #98446 (Alexey Milovidov).
• Add TPC-H benchmark suite and TPC-DS README to tests/benchmarks. #98495 (Raufs Dunamalijevs).
• Add correctness tests for all 99 TPC-DS queries. #99204 (Raufs Dunamalijevs).
• Add integration test reproducing DDL CREATE TABLE + ALTER with offline replica bug (#44070), marked as expected failure. #99259 (Raufs Dunamalijevs).
• Integrate jemalloc with je_ prefix and remove usage of linker's --wrap. #99342 (Azat Khuzhin).

ClickHouse release 26.2, 2026-02-26. Presentation, Video

Backward Incompatible Change

• Deduplication is turned ON for all inserts by default. It was OFF before for async inserts and for MV's, but it was ON for sync inserts. The goal is to have the same defaults for both ways of inserts. If you have deduplication explicitly disabled on your cluster, you have to explicitly set deduplicate_insert='backward_compatible_choice' to keep the old behavior. The same with deduplicate_blocks_in_dependent_materialized_views. #95970 (Sema Checherinda).
• Improved storage format of statistics. All statistics are now stored in a single file. #93414 (Anton Popov). If you didn't explicitly enable table statistics, you can ignore this item.
• Limit S3(Azure)Queue in-memory metadata. System tables are renamed from azure_queue to azure_queue_metadata_cache and system.s3queue to s3queue_metadata_cache. #95809 (Kseniia Sumarokova).
• Previously, applying a function to a Variant column silently returned NULLs when a variant sub-type was incompatible with the function; now it throws an exception, which may break queries that relied on the silent NULL behavior. #95811 (Bharat Nallan).
• DATE columns from PostgreSQL are now inferred as Date32 in ClickHouse (in previous versions they were inferred as Date, which led to overflow of the values outside of a narrow range). Allow inserting Date32 values back to PostgreSQL. Closes #73084. #95999 (Alexey Milovidov).
• The semantics of the do_not_merge_across_partitions_select_final setting were made more obvious. Previously, the feature could be automatically enabled when the setting was not explicitly set in the configs. It caused confusion repeatedly and, unfortunately, led to some issues in production. Now, the rules are simpler: do_not_merge_across_partitions_select_final=1 enables the functionality unconditionally. If do_not_merge_across_partitions_select_final=0, then automatic is used only if the new setting enable_automatic_decision_for_merging_across_partitions_for_final=1 and not used otherwise. To preserve the old behaviour as much as possible, the defaults were set to do_not_merge_across_partitions_select_final=0 and enable_automatic_decision_for_merging_across_partitions_for_final=1. #96110 (Nikita Taranov).
• When creating an S3 table with explicitly specified columns, ClickHouse now validates that those column names actually exist in the remote file's schema. Queries that previously worked with mismatched column names will now fail at table creation time. This closes #96089. #96194 (Konstantin Vedernikov).
• Forbid using subqueries in ORDER BY and other table key expressions. #96847 (Alexey Milovidov).
• Enable apply_row_policy_after_final by default. Initially, when optimize_move_to_prewhere_if_final=0, both ROW POLICY and PREWHERE respect FINAL and were applied after FINAL. This was broken by #87303, which ignored the optimize_move_to_prewhere_if_final for the ROW POLICY filter. To fix this, this PR enables the setting apply_row_policy_after_final introduced in #91065. With apply_row_policy_after_final enabled, ROW POLICY would continue to respect FINAL by default, as previously. This PR is an incompatible change because it changes the behaviour for optimize_move_to_prewhere_if_final=1. Now, to get the ROW POLICY applied before FINAL, apply_row_policy_after_final should be used instead of optimize_move_to_prewhere_if_final. #97279 (Nikolai Kochetov).
• The Date type is now serialized as Arrow's native date32 type in Arrow/ArrowStream formats, instead of uint16. Tools like PyArrow will now correctly see the column as a date type. The old behavior can be restored with the output_format_arrow_date_as_uint16 setting. Reading old Arrow files that used uint16 for Date columns is still supported. #96860 (Alexey Milovidov).

New Feature

• Users can now use ClickStack (an observability UI) directly from ClickHouse, useful for debugging and local development. #96597 (Aaron Knudtson).
• Support time-based one-time password (TOTP) as an authentication method. #71273 (Vladimir Cherkasov).
• Add lazy_load_tables database setting. When enabled, tables are not loaded during database startup — a lightweight StorageTableProxy is created instead and the real table engine is materialized on first access. #96283 (xiaohuanlin).
• Added input_format_max_block_wait_ms setting to emit data blocks by timeout and allowed processing of remaining data when an HTTP connection is closed unexpectedly. #94509 (Mostafa Mohamed Salah).
• Google BigLake catalog integration. This closes #95339. #97104 (Konstantin Vedernikov).
• Added system table system.tokenizers which shows all available tokenizers. #96753 (Robert Schulze).
• Add new system table system.user_defined_functions to monitor UDF loading status and configuration. #90340 (Xu Jia).
• Add system.jemalloc_stats table exposing jemalloc memory allocator statistics (via malloc_stats_print) for diagnosing memory usage on servers built with jemalloc. Also add a /jemalloc.html HTTP endpoint on the ClickHouse HTTP interface for interactive visualization of these statistics. #97077 (Antonio Andelic).
• Added system.jemalloc_profile_text table for reading and analyzing jemalloc heap profiles. The output format is controlled by the jemalloc_profile_text_output_format setting (raw, symbolized, or collapsed; default collapsed). Inline frame resolution is controlled by jemalloc_profile_text_symbolize_with_inline (when enabled, inline frames are included at the cost of slower symbolization; when disabled, they are skipped for faster output). For the collapsed format, jemalloc_profile_text_collapsed_use_count controls whether stacks are weighted by live allocation count (true) or live bytes (false, default). This enables easier memory profiling and flame graph visualization of jemalloc heap profiles. Fixes #93248. #97218 (Antonio Andelic).
• Add the default_dictionary_database setting, which lets ClickHouse resolve external dictionaries referenced without a database qualifier in a specified default database. This simplifies migration from XML-defined global dictionaries to SQL-defined per-database dictionaries—allowing existing dictionary queries (e.g. dictGet('name', …)) to continue working without modification. #91412 (Dmitrii Plotnikov).
• Support auxiliary zookeeper for DatabaseReplicated. #91683 (RinChanNOW).
• Implement new table function primes and new system table system.primes that contains prime numbers in ascending order. Closes #90839. #92776 (Nihal Z. Miaji).
• Async inserts support parallel quorum. The inserted data is replicated to the quorum. If duplicates are found, query waits until previously inserted data is replicated as well. #93356 (Sema Checherinda).
• Added functions colorOKLABToSRGB, colorSRGBToOKLAB to convert value from sRGB to OKLAB and vice versa. #93361 (Pranav Tiwari).
• A new deduplicate_insert setting which overrides insert_deduplicate and async_insert_deduplicate. #94413 (Sema Checherinda).
• Server setting insert_deduplication_version makes it possible to migrate on unified deduplication hash. #95409 (Sema Checherinda).
• Add xxh3_128 hashing function. #96055 (Raúl Marín).
• Added OPTIMIZE <table> DRY RUN PARTS <part names> query to simulate merges without committing the result part. It may be useful for testing purposes: verifying merge correctness in the new version, deterministically reproducing merge-related bugs, and reliably benchmarking merge performance. #96122 (Anton Popov).
• Add a new check enabled by default via setting check_named_collection_dependencies to avoid dropping named collections used by tables. #96181 (Pablo Marcos).
• Added system.fail_points to inspect existing failpoints in the server and whether they are enabled or not. This is going to help automate testing. #96762 (Pedro Ferreira).
• Add role-based access to Glue catalog. Use settings aws_role_arn and, optionally, aws_role_session_name. #90825 (Antonio Andelic).
• Added a setting add_minmax_index_for_temporal_columns that, when enabled, automatically creates minmax indexes for all Date, Date32, Time, Time64, DateTime, and DateTime64 columns. #93355 (Michael Jarrett).
• Support for extended table aliases for JOINs (queries like SELECT * FROM (SELECT 1) AS t(a) JOIN (SELECT 1) AS u(b) ON a = b). Closes #95131. #95331 (Yarik Briukhovetskyi).
• Added support for ALTER TABLE RENAME COLUMN for Iceberg tables. Previously only ADD COLUMN, DROP COLUMN, and MODIFY COLUMN were supported. #97455 (murphy-4o).

Experimental Feature

• The text index is now GA. #96794 (Robert Schulze).
• The QBit data type for quantized bit-packed vector storage (used for approximate nearest-neighbor search) is now generally available and no longer requires enabling an experimental setting. #95358 (Raufs Dunamalijevs).
• Vector search in ClickHouse can now use replicas in the cluster to distribute the load and search of vector index parts. This enables ClickHouse to support large vector indexes that exceed the memory capacity of a single VM. #95876 (Shankar Iyer).
• Add server-side AST fuzzer controlled by ast_fuzzer_runs and ast_fuzzer_any_query settings. When enabled, the server runs randomized mutations of each query after its normal execution, discarding the results. #97568 (Alexey Milovidov).
• Add iif function to the experimental KQL dialect. #94790 (happyso).
• Schema inference now respects allow_experimental_nullable_tuple_type. When enabled, it allows inferred tuple types to be Nullable(Tuple(...)), so missing nested objects can become NULL instead of a tuple of NULL elements. #95525 (Nihal Z. Miaji).
• The use_statistics_cache setting is now enabled by default, so column statistics are cached in memory to speed up query optimization without needing to reload them from each part. #95950 (Han Fei).

Performance Improvement

• Allow any deterministic expression in Primary Key to be used for data skipping (e.g. ORDER BY cityHash64(user_id)/ ORDER BY length(user_id)). For deterministic expressions, ClickHouse can apply the expression to query constants and use the result in the primary key index for predicates like =, IN, and has. If the expression is also injective (e.g. ORDER BY hex(p) or ORDER BY reverse(tuple(reverse(p), hex(p)))), we can effectively use the index for the negated forms: !=, NOT IN, and NOT has. Closes #10685. Closes #82161. #92952 (Nihal Z. Miaji).
• Improved storage format of statistics. All statistics are now stored in a single file. #93414 (Anton Popov).
• Allow parallelized read for remote table engines/functions in the filesystem cache. #71781 (Kseniia Sumarokova).
• Allow using userspace page cache with local files and object storage table functions. #77874 (Michael Kolupaev).
• Avoid unnecessary memcpy in userspace page cache. #77884 (Michael Kolupaev).
• The default for concurrent_threads_scheduler is now max_min_fair instead of fair_round_robin. This improves fairness under high load by prioritizing queries with fewer allocated slots, so short-running queries aren't penalized by long-running ones. #95300 (Sergei Trifonov).
• If a FINAL query used primary key condition for filtering followed by skip indexes for other conditions, the PrimaryKeyExpand processing step will now only check the initial shortlisted primary key ranges for intersection. #94903 (Shankar Iyer).
• When using parallel replicas with table functions like s3(...), queries with a single subquery wrapping the table function are now automatically parallelized across replicas, whereas previously only direct table function references were parallelized. Closes #92264. #96332 (phulv94).
• Enable splitting data and system files in cache into separate segments. #87834 (MikhailBurdukov).
• Speed up some hash join operations by implementing dynamic dispatch for ColumnVector::replicate. #79573 (Raúl Marín).
• Performance improvement for parallel hash join in cases of complex predicates. Previously, we were processing non-joined rows in one thread, which is suboptimal the idea of the optimization is to parallelize the processing of the non-joined rows across multiple threads. Can be toggled by the parallel_non_joined_rows_processing setting. Enabled by default. #92068 (Yarik Briukhovetskyi).
• Slightly optimize parsing of JSON type. #93614 (Pavel Kruglov).
• Improve memory footprint of AST. Optimization makes sense as fields are not used when highlighting is not used and there is no VALUES parsing. #93974 (Ilya Yatsishin).
• Optimize memory consumption of named Tuple AST objects. Place column names as strings in tuple object instead of having them in generic AST literal nodes. #94704 (Ilya Yatsishin).
• Devirtualization is improved with additional linker options. #94737 (Nikita Taranov).
• Improve clone replica performance for ReplicatedMergeTree tables with many parts by batching ZooKeeper requests. #94847 (c-end).
• When read step already has PREWHERE filters a new filter couldn't be added. This change postpones PREWHERE optimization until after JOIN runtime filter optimization so that runtime filters can be also pushed to PREWHERE. #95838 (Alexander Gololobov).
• Speedup T64 codec compression by using dynamic dispatch on x86. #95881 (Raúl Marín).
• Speed up uniq over numeric types by batching inserts when possible (not null, not -If, no GROUP BY, no IPv6 or String). #95904 (Raúl Marín).
• Low-level optimizations for Keeper: ZooKeeper::observeOperations has been found to account for >20% of the ZooKeeper receive thread CPU consumption. This change addresses that by: 1. For AggregatedZooKeeperLog::stats, use CityHash64 instead of SipHash which is >10x faster. 2. For Coordination::ErrorCounter, use std::array<std::atomic<UInt32>, N> instead of std::unordered_map and std::mutex. #95962 (Miсhael Stetsyuk).
• Remove 64-byte alignment for ProfileEvents::Counter to save memory. #96097 (Azat Khuzhin).
• Memory optimization: trim size of CachedOnDiskReadBufferFromFile structure 50x. #96098 (Azat Khuzhin).
• Don't copy old data on hash table resizing if it's empty. #96180 (Raúl Marín).
• Support JOIN runtime filters for RIGHT OUTER JOINs. #96183 (Hechem Selmi).
• The optimization enable_join_runtime_filters is now the default. #89314 (Alexey Milovidov).
• Previously, text index direct read optimization was applied only when all parts had a materialized text index. This PR adds partial support: if some parts have a materialized text index, those parts will use it, while parts without a materialized text index will fall back to executing the original filter expression. #96411 (Anton Popov).
• Added minmax secondary indexes on time columns and bloom_filter indexes on query_id/initial_query_id columns to system log tables for faster filtering. #96712 (Alexey Milovidov).
• Lazy materialization optimization is now applied to all branches of a UNION ALL query, not just the first one. Queries that combine multiple sorted and limited reads from different MergeTree tables via UNION ALL will now benefit from deferred column reading on every branch, reducing I/O. #96832 (Federico Ginosa).
• Optimize minmax skip index computation during INSERT by removing an unnecessary data copy and enabling vectorized min/max calculation for numeric columns. #97392 (Raúl Marín).
• Storage DeltaLake now takes count() result from delta lake metadata and shows correct table stats in system.tables (total bytes/rows). #96190 (Kseniia Sumarokova).
• The unused columns are removed also from the reading step in case of reading from a MergeTree. It is especially useful when a filter is pushed down into PREWHERE. #89982 (János Benjamin Antal).
• Improved processing SHOW TABLES query by fetching only names of tables and improved getLightweightTablesIterator to return structure containing only table names. resolves #93835. #94467 (Smita Kulkarni).
• Improve assumeNotNull, coalesce, ifNull to enable primary key and skip index pruning for range predicates when key columns are wrapped in these functions. Closes #94689. #94754 (Nihal Z. Miaji).
• Add with_data & with_stat extension to getChildren Keeper request. This allows fetching not only the list of children, but also their stat and/or data in a single operation. #94826 (Nikolay Degterinsky).
• The index analysis is done only once (in most cases) regardless of whether we end up executing a local plan or a plan with parallel replicas. #94854 (Nikita Taranov).
• Allow to enable distributed index analysis based on amount of parts (distributed_index_analysis_min_parts_to_activate) and indexes size (distributed_index_analysis_min_indexes_size_to_activate). #95216 (Azat Khuzhin).
• Enable PREWHERE optimization for Iceberg tables. #95476 (Konstantin Vedernikov).
• Reduce the memory footprint of some AST classes. #95514 (Raúl Marín).
• Limit the number of pipeline streams generated with split_intersecting_parts_ranges_into_layers enabled. Helps to avoid excessive memory consumption. #96478 (Nikita Taranov).
• Implement equivalent sets optimization for multiple joins. Queries with multiple consecutive INNER JOIN operations now benefit from improved filter pushdown optimization. When tables are joined on equivalent columns (e.g., t1 JOIN t2 ON t1.id = t2.id JOIN t3 ON t2.id = t3.id WHERE t1.id > 10), filters applied to any table in the chain are automatically pushed down to all tables. Close #96550. #96596 (Vladimir Cherkasov).
• Optimize delta lake metadata scan. Uses changes from delta-kernel PR https://github.com/delta-io/delta-kernel-rs/pull/1827. #96686 (Kseniia Sumarokova).
• In Replicated database, don't update the cached cluster for every dummy query. #96897 (Tuan Pham Anh).
• Use the primary key index when filtering with startsWithUTF8 if the prefix contains only ASCII characters. #97055 (vkcku).

Improvement

• Add OpenTelemetry tracing for Keeper requests. #91332 (Miсhael Stetsyuk).
• New configuration options: logger.startup_console_level & logger.shutdown_console_level to allow for overriding the console log level during the startup & shutdown of ClickHouse respectively. #95919 (Garrett Thomas).
• Respect command-line overrides when reloading configuration. Closes #80294. #80295 (Alexey Milovidov).
• Allow key-value overrides for named collection parameters in mongodb table function. #89616 (vanchaklar).
• The read-in-order optimization for Iceberg tables now works with complex sorting functions like icebergBucket and icebergTruncate, not just simple column references. #90256 (Konstantin Vedernikov).
• Add a new column named parts_postpone_reasons in system.mutations to improve diagnostics, which shows the parts postpone reasons. #92206 (Shaohua Wang).
• Track changes in the number of rows to read (due to inserts/deletes or query condition cache usage) in DataflowStatisticsCache. #93636 (Nikita Taranov).
• Support SYSTEM RESET DDL WORKER [ON CLUSTER] query. It requests to reset the state of DDLWorker in its main thread. It is helpful to refresh the replica active when host IDs are updated. #93780 (Tuan Pham Anh).
• Support mutation_ids in system.part_log for event type of MUTATE_PART and MUTATE_PART_START. #93811 (Shaohua Wang).
• Background operations (Mutate, Merge) can now be configured independently via 'background' profile. Previously such operations shared settings with regular queries via 'default' profile. #93905 (Arsen Muk).
• Add more information to system.crash_log. #94112 #95857 (Miсhael Stetsyuk).
• Added new QueryNonInternal metric to track the number of executing non-internal queries. This metric is exposed as ClickHouseMetrics_QueryNonInternal and helps operators monitor query concurrency against the max_concurrent_queries limit, which only applies to non-internal queries. #94284 (Ashwath Singh).
• Support input bytes statistics collection for columns from compact parts in RuntimeDataflowStatisticsCacheUpdater. #94626 (Nikita Taranov).
• Add a check for Keeper misconfiguration leading to cluster assembly failures. Closes #60932. #94682 (Konstantin Bogdanov).
• Improve JSON prefixes deserialization during part loading. #94848 (Pavel Kruglov).
• Refactor the write using full INSERT pipeline, which triggers materialized views on the target table. #94890 (Kai Zhu).
• Use vector similarity search plan optimizations only if the index exists for the search column. #94998 (Eduard Karacharov).
• Check for the total memory limit before the user authentication and throw (total) memory limit exceeded if the total limit is more than allowed. #95003 (Nikolai Kochetov).
• Added the throw_on_unmatched_row_policies configuration option which, when enabled, throws an exception if a user queries a table that has row policies but none of them apply to that user — preventing the ambiguous behavior of returning all rows due to access control misconfiguration. #95014 (Vitaly Baranov).
• Dynamic update s3 access tokens in long queries with unity catalog. This closes #93981. #95069 (Konstantin Vedernikov).
• Disable jemalloc's dirty page decay if ClickHouse is under sustained memory pressure for memory_worker_decay_adjustment_period_ms milliseconds. Enable jemalloc's dirty page decay back if ClickHouse is working under normal conditions for same amount of time. #95145 (Antonio Andelic).
• S3Queue auxiliary Zookeeper support using keeper_path setting from s3Queue. #95203 (Diego Nieto).
• Respect max_parts_to_merge_at_once in TTL drop part merges. #95315 (Kseniia Sumarokova).
• Add connection_address and connection_port to query_log to reflect physical connection (address and port are replaced when connected through proxy and auth_use_forwarded_address=1). #95471 (Yakov Olkhovskiy).
• Fix incorrect memory accounting for the query conditions cache. The key problem was that it didn't take into account the cache key that composed of several strings (like part_name, the table id and the whole SQL condition). #95478 (Nikita Mikhaylov).
• Server started with the embedded configuration will allow to manipulate users and grants, saving them to the access directory, as the regular configuration does. This improves testing. Also enabled all access_control_improvements in the embedded config and in clickhouse-local. #95481 (Alexey Milovidov).
• Improved S3 authentication error messages to include a hint to check credentials when access is denied. #95648 (Gerald Latkovic).
• Enable statistics cache and set the update period of cache to 300s. #95841 (Han Fei).
• Add component name to system.aggregated_zookeeper_log. #95882 (Antonio Andelic).
• Skip object storage reads when querying DeltaLake tables from system.tables. #95899 (Antonio Andelic).
• Enable enable_max_bytes_limit_for_min_age_to_force_merge by default if the compatibility setting is 26.2 or higher. #95917 (Christoph Wurm).
• Delta Lake is now available on macOS. Closes #95979. #95985 (Alexey Milovidov).
• In previous versions, when combining conflicting ALTER expressions with UPDATE and RENAME COLUMN, a logical error was thrown instead of a proper exception. Closes #70678. #96022 (Alexey Milovidov).
• Improve the help output for all ClickHouse applications and add a --no-sudo option with a few fixes. This is a continuation of #58244 from Ilya Yatsishin. #96025 (Alexey Milovidov).
• Add distanceCosine alias for cosineDistance because all other distance functions already have alias of this form. #96065 (Raufs Dunamalijevs).
• Add support for the with_data Keeper extension to improve table fetching in Database Replicated. #96090 (Nikolay Degterinsky).
• Update chdig to v26.2.1 (new features and MacOS support). #96113 (Azat Khuzhin).
• Improve filter pushdown for numbers and primes. ClickHouse can now derive conservative value bounds from WHERE conditions when exact bounds cannot be derived, and restrict sequence generation accordingly (for example, for WHERE number % 5 < 2 AND number > 100 AND number < 300, ClickHouse will only generate numbers between 100 and 300, then apply the predicate), avoiding unbounded scans. Closes #84853. Closes #93913. #96115 (Nihal Z. Miaji).
• The formatter previously wrapped SELECT in parentheses when a COMMENT clause was present to disambiguate parsing. Instead, output COMMENT before AS SELECT, which eliminates the ambiguity without parentheses. #96293 (Alexey Milovidov).
• The allow_impersonate_user config setting is now located inside the access_control_improvements section rather than being a standalone server setting. #96451 (Vitaly Baranov).
• Make core_dump.size_limit configuration setting hot-reloadable, to avoid having to restart servers for configuration changes to take place. #96524 (Miсhael Stetsyuk).
• Improves CPU and real-time profiler interoperability with socket timeouts. #96601 (Sergei Trifonov).
• Prevent the resurrection of dropped data if ADD COLUMN is run quickly after the DROP COLUMN mutation. #96713 (Alexey Milovidov).
• Change function_id type in system.instrumentation from LowCardinality(Int32) to Int32. #96726 (Copilot).
• Synchronous waiting for mutations will respect query cancellation and time limits. #96756 (Alexey Milovidov).
• Added system command SYSTEM RELOAD DELTA KERNEL TRACING <level> to be able to change delta-kernel logging, which can be useful for debugging. #96763 (Kseniia Sumarokova).
• Filtering by IP address family, i.e. dns_allow_resolve_names_to_ipv4/ipv6 settings, are applied even if DNS cache is disabled. #96810 (c-end).
• Better jemalloc introspection. #96840 (Azat Khuzhin).
• Fix /play Web UI throwing QUERY_CACHE_USED_WITH_SYSTEM_TABLE when querying system tables. #96869 (Alexey Milovidov).
• Improve Web UI: change favicon to indicate running query state; display errors from auxiliary queries (loading databases and tables) instead of silently ignoring them. Closes #85055. #96883 (Alexey Milovidov).
• Make the left panel in /play UI clickable to toggle the database list. #96884 (Alexey Milovidov).
• DROP DATABASE now drops tables in reverse dependency order, improving crash-safety when the database contains tables with loading dependencies (e.g. Distributed tables using joinGet). #97057 (Alexey Milovidov).
• Bump yaml-cpp to prevent skipping invalid YAML. #97333 (Azat Khuzhin).
• Show a loading indicator in the play.html sidebar while tables are being fetched. #97531 (Alexey Milovidov).
• Add a copy-to-clipboard button for raw query results in the built-in web UI (play.html). #97532 (Alexey Milovidov).
• Fix query obfuscator (clickhouse-format --obfuscate) to produce parseable SQL in more cases. #97584 (Alexey Milovidov).

Bug Fix (user-visible misbehavior in an official stable release)

• After metadata-only ALTERs, such as extending the elements of Enums, the optimization of aggregation with projection may end up producing an exception. #84143 (Alexey Milovidov).
• Materialized views now use the database where they were created as execution context, meaning that: - it is possible to omit explicit database qualification on names referred in view's select query - if no explicit database qualification is given, the same database where the materialized view was created is assumed. #88193 (Dmitry Kovalev).
• Fix query parameter substitution in CREATE USER authentication methods when using ON CLUSTER. Query parameters in authentication methods (e.g., password) were not being replaced, causing UNKNOWN_QUERY_PARAMETER errors on remote nodes. #92777 (xiaohuanlin).
• Fixed inconsistencies in text index analysis for has, mapContainsKey, and mapContainsValue functions. Previously, queries using these functions could return different results depending on whether the expression was evaluated with or without a text index. #93578 (Anton Popov).
• Fix crash when attaching a table to a MaterializedPostgreSQL database if dropReplicationSlot throws during stack unwinding. #96871 (Alexey Milovidov).
• Backups could crash the server if you do many concurrent backups clashing over the same files. #93659 (Alexey Milovidov).
• Fixes queries with parallel replicas and JOIN with non-MT table. Closes #92056. #93902 (Igor Nikonov).
• Fixes an issue when Iceberg columns with dot in names returned NULL as values. #94335 (Mikhail Koviazin).
• Fixed handling of UTF8 strings in stringJaccardIndexUTF8 and improve performance. #94613 (Joanna Hulboj).
• Fix possible overflows in WITH FILL STALENESS (that leads to UB or/and endless loops). Fix possible endless loop due to big jumps. Add old analyzer support (mostly for stress tests). #94663 (Azat Khuzhin).
• Fix possible hung distributed queries when hostnames resolve to multiple addresses and a remote replica freezes. #94726 (c-end).
• Fix invalid result on joining multiple table expressions, when leftmost table expression is a -Cluster table function. Resolves #89996. #94748 (Konstantin Bogdanov).
• Fix incorrect primary key and skip index pruning for predicates involving toWeek, toYearWeek, toStartOfWeek, toLastDayOfWeek, and toDayOfWeek, and fix exceptions in some of these functions for valid queries with LowCardinality(String). #94816 (Nihal Z. Miaji).
• Remove unnecessary skip permissions check in ATTACH queries for a view with SQL Security. This prevents potential privilege escalation when a user attaches a view with a definer without validating required access. #94865 (pufit).
• Fixes a crash during ReplicatedMergeTree startup caused by concurrent removal of delete_tmp_* directories. #94892 (myeongjun).
• Fix INSERT into Iceberg tables with materialized views losing deduplication information, which caused an exception. #94938 (Daniil Ivanik).
• Fix a bug where SYSTEM DROP QUERY CACHE TAG 'TAGNAME' ON CLUSTER <CLUSTERNAME> would drop the full cache on the cluster. #94978 (Rory Crispin).
• Preserve constant index granularity (use_const_adaptive_granularity) after Vertical merges (v2 with a fix for Nested, and in general). #95013 (Azat Khuzhin).
• Fixes race in filesystem cache in version 26.1 after [ClickHouse/ClickHouse#82764](https://github.com/ClickHouse/ClickHouse/pull/82764). #95042 (Kseniia Sumarokova).
• Fix postgresql() table function canceling by KILL QUERY and cancel query (Ctrl+C) in clickhouse-client. #95136 (Roman Vasin).
• Fixed type inference for qualified columns from source tables when multiple joins are used with USING clause. Previously, subsequent joins incorrectly updated types of underlying source columns to a common supertype even when the column was not involved in that join (e.g., in SELECT t2.a FROM t1 LEFT JOIN t2 USING (a) LEFT JOIN t3 USING (a), the t2.a column is only used by the first join, so its type should be the supertype of t1.a and t2.a, excluding t3.a). This could lead to logical errors or crashes when functions expected different column types than what actually appeared in the execution plan. #95157 (Vladimir Cherkasov).
• Make column transform only once during getting content of manifest .avro list and files. #95164 (Daniil Ivanik).
• Fix incorrect calculation of JSON column sizes that could lead to excessive memory usage or wrong column statistics. #95207 (Azat Khuzhin).
• Fixed inaccurate memory accounting when applying large patch parts after lightweight updates. Previously, applying large patches could cause excessive memory usage and result in the server process being killed by the OOM killer. #95231 (Anton Popov).
• Fix undefined behavior that could cause incorrect results or an exception when a distributed query with max_parallel_replicas fell back to a local replica during index analysis. #95263 (Azat Khuzhin).
• Fix aggregation of sparse columns for sum and timeseries when group_by_overflow_mode is set to any. #95301 (Mikhail Koviazin).
• Fix a reliability issue in plain_rewritable disk policy where a network error mid-way through unlinking a metadata file could leave the storage in an inconsistent state. #95302 (Mikhail Artemenko).
• Replace Date with Date32 for iceberg. #95322 (Konstantin Vedernikov).
• The password argument of the redis table function now will be masked in the logs and system tables (e.g.: query_log). #95325 (János Benjamin Antal).
• Fix a bug where tables could be dropped or altered while a distributed query was still executing against them, potentially causing exceptions or incorrect results. #95356 (Azat Khuzhin).
• Fix a logical error in some cases when negative LIMIT/OFFSET is used in distributed queries. #95357 (Nihal Z. Miaji).
• Fix a bug where clickhouse-client would ask for password twice when connecting using ssh. #95372 (Isak Ellmer).
• Fix a data race in storage S3(Azure)Queue. #95385 (Kseniia Sumarokova).
• Fix the prewhere filter error caused by lambda expressions in prewhere. #95395 (Xiaozhe Yu).
• Fix optimize_syntax_fuse_functions to not rewrite sum/count/avg into sumCount() when the aggregate argument is Nullable. Closes #95390. #95441 (Nihal Z. Miaji).
• Avoid possible crash for distributed queries in case of cancellation. #95466 (Aleksandr Musorin).
• Fix deduplication for streaming from S3(Azure)Queue engine. #95467 (Kseniia Sumarokova).
• Fix updating row policies assigned to the initial user in distributed queries. #95469 (Vitaly Baranov).
• Fix check for encrypted disks over plain_rewritable (Fixes possible It is not possible to register multiple plain-rewritable disks with the same object storage prefix). #95470 (Azat Khuzhin).
• The mergeTreeProjection table function was missing an access check, allowing users without SELECT permission on a table (but with permissions for table functions) to read data from its projections. This fix adds the same access check that mergeTreeIndex and mergeTreeAnalyzeIndexes already have. #95480 (Alexey Milovidov).
• Fix possible logical error during reading of size subcolumn from dynamic subcolumns of Dynamic/JSON types. #95573 (Pavel Kruglov).
• Fix regression in (experimental) zero‑copy replication introduced by #94262 where shared parts could be deleted before other replicas finished fetching them. #95597 (filimonov).
• Fix crash during tupleElement applied to arrays of JSON. Closes #95581. #95647 (Pavel Kruglov).
• Fix logical error exception when using a matcher (*) inside a lambda function within a VALUES clause in a JOIN with USING. Close #93675. #95661 (Vladimir Cherkasov).
• Fixed There was an error: Cannot obtain error message logical error when waiting for a distributed DDL and dropping the Replicated database concurrently. Fixes #95539. #95664 (Alexander Tokmakov).
• Fix IN function returning incorrect results with NULL values when transform_null_in is enabled. Closes #65776. #95674 (Nihal Z. Miaji).
• Correctly handle LowCardinality Nullable types in CAST when the setting cast_keep_nullable is enabled. Closes #95670. #95747 (Alexey Milovidov).
• Fix squashing partitioned delta lake data. #95773 (Kseniia Sumarokova).
• Fix race condition for Nullable join column in runtime filters. #95775 (Hechem Selmi).
• Fix possible logical error in query with matcher (*, table.*) and analyzer_compatibility_join_using_top_level_identifier when USING column has different types in tables and select list. Close #90477. #95808 (Vladimir Cherkasov).
• Fix memory safety bugs in parallel thread pool operations (backups, aggregation, distributed queries) that could cause exceptions when an error occurred during task scheduling. #95818 (Raúl Marín).
• Fixes a crash on the DROP WORKLOAD while running concurrently with queries using the workload being dropped. #95856 (Alexey Milovidov).
• Fix slow performance when querying system tables with a user that has limited grants on many databases. Closes #89371. #95874 (pufit).
• Fix executing tupleElement on JSON with nested paths, previously it could lead to wrong query result. #95907 (Pavel Kruglov).
• Fixed a NOT_SUPPORTED error that could occur when using the direct join algorithm with an empty MergeTree table. #95935 (Vladimir Cherkasov).
• Fix the client not suggesting and auto-completing alias names for settings, closes #92190. #95945 (phulv94).
• Fix event_date in system.asynchronous_metric_log. #95947 (Raúl Marín).
• Fix skipping paths in JSON data type. Previously with JSON(SKIP path) all JSON keys with prefix path were skipped, even keys like "pathpath", so it could lead to data loss for these paths during insert. Now it's fixed and only key "path" is skipped. #95948 (Pavel Kruglov).
• Part with unknown projections should not be marked as lost forever. #95952 (Mikhail Artemenko).
• Fix empty string becoming NULL in Join table with Nullable(String) key. Closes #71414. #96002 (Alexey Milovidov).
• Now the PostgreSQL engine can correctly read BOOLEAN[]. Closes #72754. #96006 (Alexey Milovidov).
• Fix the ProtobufList format for the case of reading from an empty file. Closes #70059. #96007 (Alexey Milovidov).
• Fix ProtobufList format producing ghost record for empty tables. Closes #72596. #96010 (Alexey Milovidov).
• Fix if function type mismatch between UInt64 and Int32 in an unusual case of distributed queries and PREWHERE, with type inference. Closes #70017. #96012 (Alexey Milovidov).
• Fix JIT compiled queries involving Bool types. #96013 (Alexey Milovidov).
• Fix logical error when reading UUID column from SQLite TEXT column. Closes #71263. #96016 (Alexey Milovidov).
• Fix SQLite engine type conversion for DateTime, Date, UUID, and other types. Closes #73481. #96017 (Alexey Milovidov).
• FixedString values were escaped incorrectly in queries to external databases, SQLite and PostgreSQL. Closes #73519. Co-authored with @jh0x. #96019 (Alexey Milovidov).
• Fix assertion failure in WindowTransform with a large PRECEDING offset. Closes #75852. #96026 (Alexey Milovidov).
• Fix a bug with possible data corruption when concurrent async inserts are using the same parameter names but contain different values. #96035 (Seva Potapov).
• Fix period for global profilers (controlled by global_profiler_real_time_period_ns and global_profiler_cpu_time_period_ns). Instead of set value, a truncated value was used, causing profiler to wakeup more than intended. #96048 (Antonio Andelic).
• Earlier if reference data file inside iceberg manifest file for position delete was present in an entry but was null, we didn't get correct bounds for a corresponding data files. This PR fixes this bug. #96061 (Daniil Ivanik).
• Fix revoking default roles. #96103 (Vitaly Baranov).
• Fix use-after-free in the index analysis in a rare combination of disabled use_primary_key and a very large number of disjunctions of conditions that use the index. #96112 (Alexey Milovidov).
• Fix a regression with the Gorilla codec when an explicitly specified size does not correspond to the data type size, and the buffer size is too small. In previous versions, it threw an exception on decompression. Closes #78253. #96118 (Alexey Milovidov).
• Avoid a deadlock in dictionaries loaded when one dictionary references a Merge table that references it recursively. Closes #78360. #96120 (Alexey Milovidov).
• Fix use-of-uninitialized-value in formatDateTime with non-fixed-width formatters, such as MySQL and JODA-style. #96133 (Alexey Milovidov).
• The combination of settings use_const_adaptive_granularity and index_granularity_bytes (which means "non-adaptive granularity") led to a miscalculation of the number of rows to read and an exception. #96143 (Alexey Milovidov).
• Running an invalid ALTER UPDATE mutation on object storage file-like tables, such as S3 and Azure, could lead to a nullptr dereference. Closes #92994. #96162 (Alexey Milovidov).
• Fix AccessRights::contains returning incorrect results with partial revokes. #96170 (pufit).
• Fix query condition cache hash collision for CTE folded constants, which could lead to a wrong query result. Closes #96060. #96172 (Alexey Milovidov).
• Fix possible deadlock in ProcessList. It can happen because of possible lock inversion if memory overcommit tracker triggers when we are adding task to cancellation checker. #96182 (Antonio Andelic).
• Fixed a bug where queries involving outer joins (LEFT, RIGHT, or FULL) combined with multiple INNER JOINs could return incorrect results due to illegal join reordering. When an outer join's ON condition referenced columns from multiple previously joined tables, the optimizer failed to account for all table dependencies and could reorder the joins incorrectly, producing missing rows. Close #95972. #96193 (Vladimir Cherkasov).
• When a table has no statistics defined, ClickHouse shouldn't try to load them. This avoids some overhead (100+ms) for checking if the statistics files exist. (issue #96068). #96233 (Han Fei).
• Fix optimize_syntax_fuse_functions to not rewrite sum/count/avg into sumCount() when the aggregate argument is LowCardinality(Nullable). Closes #95390. #96239 (Nihal Z. Miaji).
• Fix incorrect partition pruning for not IN and not has function in some cases. #96241 (Nihal Z. Miaji).
• Fix stack-use-after-scope in the vector similarity index. #96259 (Alexey Milovidov).
• Fix test runner not recognizing error hint comments when a query is preceded by a SQL comment. #96336 (Yakov Olkhovskiy).
• Fix logical error in KeyCondition when a table has a nullable primary key, and the query uses the coalesce function, which has its first argument constant. #96340 (Alexey Milovidov).
• The interaction of GROUPING SETS, group_by_use_nulls, and the Tuple data type with LowCardinality inside it, could produce an unexpected block structure in the query pipeline, which led to a logical error. This appeared after the introduction of Nullable Tuples. #96358 (Alexey Milovidov).
• It was possible to create a table with an empty expression () as an index, which led to an invalid memory access. #96363 (Alexey Milovidov).
• Fixed crash in old analyzer if JOIN and duplicated aliases. #96405 (Ilya Golshtein).
• Fix Nested columns sizes are inconsistent with local_discriminators error due to a wrong in-place filtering optimization for Variant columns. #96410 (Alexey Milovidov).
• Fix CREATE TABLE ... CLONE AS ... ignoring full qualifier of source table. #96415 (Hasyimi Bahrudin).
• Fix mysql table function canceling by KILL QUERY and cancel query (Ctrl+C) in clickhouse-client. #96437 (Roman Vasin).
• Fixes livelock in the cancellation checker thread for queries with high max_execution_time values. #96450 (Sergei Trifonov).
• Fix a logical error in some cases when fractional LIMIT/OFFSET is used in distributed queries. #96475 (Nihal Z. Miaji).
• Fix null pointer dereference in certain expressions with lambda functions. #96479 (Alexey Milovidov).
• Fix incorrect results when LowCardinality columns are converted to Nullable. #96483 (Nihal Z. Miaji).
• Fix a crash when creating an Iceberg table with an ORDER BY clause referencing a non-existent column or using a positional argument. Closes #93280. #96484 (Konstantin Vedernikov).
• Fix runtime filter exception for Tuple columns with Nullable subfields. #96509 (Alexey Milovidov).
• Fix LOGICAL_ERROR exception in Parquet V3 native reader when PREWHERE filter column contains non-boolean UInt8 values. #96594 (Alexey Milovidov).
• Fix implicit index regeneration in replicated tables during metadata changes. #96600 (Raúl Marín).
• Fixes a datarace on DROP WORKLOAD. #96614 (Sergei Trifonov).
• Fix a bug in Iceberg table writes where partitioned inserts could produce incorrect data distribution across partition files. #96620 (Konstantin Vedernikov).
• Fixed heap-use-after-free in CREATE TABLE with constraints. #96669 (Nikita Taranov).
• Validate witness version in bech32 to avoid buffer overflow. #96671 (Raúl Marín).
• Fix system.tables returning errors when a Data Lake REST catalog is created with an invalid auth_header setting. #96680 (Han Fei).
• Fix min(timestamp) returning epoch (1970-01-01) via _minmax_count_projection after TTL merge when all rows in a block are filtered out. #96703 (Raquel Barbadillo).
• Improve validation of the iceberg_metadata_file_path setting to prevent path traversal and ensure the specified metadata file is within the table directory. #96754 (Daniil Ivanik).
• Fix crash in ifNull with Variant argument used in GROUP BY. #96790 (Alexey Milovidov).
• Fixed cache key collisions between tables with table_disk=1 setting. #96818 (Raufs Dunamalijevs).
• Fix MemoryWorker's purging thread being stuck because of a race condition. #96819 (Antonio Andelic).
• Don't log data with credentials in iceberg catalogs. #96831 (Konstantin Vedernikov).
• Fix exit status of clickhouse-client after server error. #96841 (Vitaly Baranov).
• Queries with CROSS JOINs and enabled parallel replicas could return incorrect result. Fixes #74337. #96848 (Igor Nikonov).
• Fixed ALTER TABLE DROP COLUMN queries failing after a lightweight update was previously performed on the same column. #96861 (Anton Popov).
• Fix stack overflow (crash) when creating archive-based backups (.zip, .tzst) to a plain_rewritable object storage disk. #96872 (Alexey Milovidov).
• Fix server crash when backup fails due to full disk or other I/O errors on the destination filesystem. #96873 (Alexey Milovidov).
• Fix EXCEPT ALL and INTERSECT ALL ignoring row multiplicities and behaving like their DISTINCT counterparts. #96876 (Alexey Milovidov).
• Fix std::terminate exception in indexOfAssumeSorted when called with incompatible types (e.g., IPv4 array with integer search value). #96877 (Alexey Milovidov).
• Fix exception Bad cast from type DB::ColumnNullable to DB::ColumnString when using window functions with group_by_use_nulls = 1 and CUBE/ROLLUP/GROUPING SETS. #96878 (Alexey Milovidov).
• Fix incorrect results when JIT-compiled expressions convert DateTime to DateTime64 (e.g., in CASE/if/multiIf with mixed DateTime types). The value was reinterpreted instead of properly scaled, producing wrong timestamps after expression compilation kicked in. #96879 (Alexey Milovidov).
• Fix logical error exception in CoalescingMergeTree when a skip index expression produces a constant column (e.g., bloom_filter on ifNotFinite(1, c0) for an integer column). #96880 (Alexey Milovidov).
• Fix wrong port number in error message when accidentally connecting with HTTP to the TLS-enabled native protocol port. #96881 (Alexey Milovidov).
• Fix per-subquery SETTINGS not being applied to table functions like file in CTEs and subqueries. #96882 (Alexey Milovidov).
• Fix memory leak of BIO objects when reading X509 certificates. #96885 (Alexey Milovidov).
• Fix LOGICAL_ERROR exception in query analyzer when a lambda expression is passed where a concrete value is expected (e.g., as the accumulator argument of arrayFold). #96892 (Alexey Milovidov).
• Fix ColumnNullable is not compatible with original exception when casting complex nested types (Array of Nullable Tuple containing Map with Nullable Enum values). #96924 (Alexey Milovidov).
• Fix a race condition in sharded HASHED dictionary parallel loading that could occasionally cause some rows to not be loaded. #96953 (Alexey Milovidov).
• Fix a race condition between REPLACE PARTITION and background mutations that could result in both old and new data being visible after the replace. #96955 (Alexey Milovidov).
• Fix arrayJoin function producing duplicate rows when used with INNER JOIN and WHERE clause, caused by the partial predicate push-down optimization incorrectly pushing filters containing arrayJoin below a JOIN. #96989 (Alexey Milovidov).
• Fix crash (SEGFAULT) in clearCaches caused by BlockIO::operator= not moving query_metadata_cache, leading to premature destruction of cached storage snapshots and use-after-free of MergeTreeData storage. #96995 (Alexey Milovidov).
• Fix assertion failure in IfTransformStringsToEnumPass when the if or transform function returns Nullable(String) (e.g. with GROUP BY ... WITH CUBE and group_by_use_nulls = true). #97002 (Alexey Milovidov).
• Fix incorrect data written during INSERT ... SELECT with UNION ALL and JOIN, where constant string columns could receive wrong values after block squashing. #97019 (Hasyimi Bahrudin).
• Fix assert_cast exception (or silent data corruption in release builds) when building column statistics after ALTER TABLE MODIFY COLUMN changes the column type. #97027 (Alexey Milovidov).
• Fix reads of uninitialized memory in Azure Blob Storage, SSH protocol, and Arrow Flight interfaces. #97053 (Alexey Milovidov).
• Fix cases where indexes were affecting the result for queries with row policy/PREWHERE and FINAL. #97076 (Yarik Briukhovetskyi).
• Fix remaining race condition between REPLACE PARTITION and background mutations in MergeTree tables that could cause old data to reappear. #97105 (Alexey Milovidov).
• Fix implicit indices with alias columns and do full validation before creating them. #97115 (Raúl Marín).
• Fix logical error in FunctionVariantAdaptor with functions requiring const arguments like arrayROCAUC. #97116 (Bharat Nallan).
• Fix stuck mutations when PartCheckThread re-enqueues a GET_PART for an already-mutated part, leaving phantom entries in parts_to_do. #97162 (Alexey Milovidov).
• Fix query plan row count estimation for subqueries with ORDER BY ... LIMIT, which could cause the optimizer to choose a suboptimal join order. #97193 (Alexander Gololobov).
• Fix LOGICAL_ERROR exception in FunctionVariantAdaptor when a function operating on Variant columns returns Nothing type, which can happen with empty arrays in UNION ALL queries. #97213 (Alexey Milovidov).
• Fix a data race during S3 multipart copy operations (e.g., during BACKUP/RESTORE to S3) that could cause exceptions under concurrent access. #97227 (Azat Khuzhin).
• Fix LOGICAL_ERROR exception when arrayJoin in WHERE clause references columns from both sides of a JOIN. #97239 (Alexey Milovidov).
• Fix LOGICAL_ERROR exception when reading .size subcolumn of a sparse Nullable(String) in a Tuple with PREWHERE. #97264 (Alexey Milovidov).
• Fix exception "Number of rows in lazy chunk does not match number of offsets" in LazyMaterializingTransform when reading from tables with non-adaptive index granularity (index_granularity_bytes = 0) using ORDER BY ... LIMIT. #97270 (Alexey Milovidov).
• Fix SYSTEM RESTART REPLICA losing table from database when table re-creation fails with a non-ZooKeeper exception (e.g. memory limit), causing metadata digest mismatches in DatabaseReplicated. #97276 (Alexey Milovidov).
• Field readonly in system.merge_tree_settings now properly reflects that certain merge tree settings (e.g. index_granularity) are unconditionally readonly. #97277 (Robert Schulze).
• Fix a crash during count() optimization on MergeTree tables when the storage snapshot was created without data. #97281 (Pablo Marcos).
• Fix a possible crash when resolving function names from debug information for stack traces. #97294 (Azat Khuzhin).
• Fix logical error with analyzer_compatibility_join_using_top_level_identifier and ALIAS columns. Close #96228. #97297 (Vladimir Cherkasov).
• Fix LOGICAL_ERROR exception in applyOrder when using text-indexed columns with QUALIFY clause. #97313 (Alexey Milovidov).
• System table system.functions now shows for internal functions categories = 'Internal' instead of categories = ''. #97315 (Robert Schulze).
• Query with RIGHT JOIN chain and enabled parallel replicas can produce incorrect result. Fixes #74341. #97316 (Igor Nikonov).
• Fix spurious TABLE_UUID_MISMATCH errors that could occur with refreshable materialized views and other scenarios where tables are renamed. #97323 (Azat Khuzhin).
• Fix segfault in StorageKeeperMap backup due to use-after-free of dangling storage pointer in lazy backup batch. #97336 (Alexey Milovidov).
• Fix the exists function with a scalar subquery inside an ALTER UPDATE/DELETE when mutations_execute_subqueries_on_initiator is enabled. The scalar subquery was incorrectly evaluated, which could lead to an error or a corrupt mutation command that made the table unloadable on the next server restart. #97347 (Kirill Kopnev).
• Fix logical exception Unexpected return type from equals. Expected Nullable(UInt8). Got Const(LowCardinality(Nullable(UInt8))) when comparing NULL with a Variant column containing LowCardinality types. #97379 (Alexey Milovidov).
• Fix a possible race condition when EXCHANGE TABLES is executed in parallel with the sharded query cache enabled. #97411 (Konstantin Vedernikov).
• Fix LOGICAL_ERROR exception in Array-to-QBit conversion when nullable_source from an outer Tuple wrapper replaces the converted array column with a mismatched column type. Closes #97389. #97413 (Alexey Milovidov).
• Fix AST formatting roundtrip inconsistency for aliased tuple literals inside parentheses, e.g., (('a', 'b') AS x) was incorrectly reformatted as tuple(('a', 'b') AS x). #97418 (Alexey Milovidov).
• Fix an exception during asynchronous inserts with deduplication when a parsing failure produced an empty block with zero rows. #97460 (Sema Checherinda).
• Fix exception "Number of rows in lazy chunk does not match number of offsets" in LazyMaterializingTransform when reading from tables with non-adaptive index granularity (index_granularity_bytes = 0) using ORDER BY ... LIMIT. #97482 (Alexey Milovidov).
• Fix insert iceberg settings. Add alias for the allow_experimental_insert_into_iceberg setting. #97483 (Konstantin Vedernikov).
• Fix ACCESS_DENIED for users without CREATE TEMPORARY TABLE permission when optimize_inverse_dictionary_lookup optimization rewrites dictGet(...) predicates. ClickHouse now skips the rewrite and executes the original expression. Closes #97269. #97484 (Nihal Z. Miaji).
• Fix assertion failure (exception in debug/sanitizer builds) in Set and MergeTreeIndexSet when processing columns with inner sparse subcolumns (e.g., Tuple columns from MergeTree parts with different sparse serialization profiles). #97493 (Alexey Milovidov).
• Fix a possible use after free in StorageKafka2. #97520 (Bharat Nallan).
• Fix INTO OUTFILE with TRUNCATE and into_outfile_create_parent_directories setting when the output path contains directories. #97549 (Alexey Milovidov).
• Fix BAD_ARGUMENTS error when querying tables with lambda expressions inside ALIAS columns through the merge() table function with the analyzer enabled. #97551 (Alexey Milovidov).
• Fix system.zookeeper_info exception when Keeper zxid is 0. #97553 (Alexey Milovidov).
• Fix a possible logical error in ip_trie dictionary when key type is not String. #97555 (Bharat Nallan).
• Fix REST catalog OAuth authentication not working for the base RestCatalog (it only worked for derived catalogs like OneLakeCatalog). This broke the default REST catalog after BigLake catalog was introduced. #97561 (Konstantin Vedernikov).
• Geometry functions (perimeterSpherical, areaSpherical, etc.) now accept individual geometry subtypes (Polygon, Ring, Point, etc.) in addition to the Geometry variant type. #97571 (Alexey Milovidov).
• Fix LOGICAL_ERROR exception when using isNull/isNotNull on subcolumns of Nullable(Tuple(... Nullable(T) ...)) types. Closes #97224. #97582 (Alexey Milovidov).
• Fix null pointer dereference when applying patch parts during lightweight updates. #97583 (Alexey Milovidov).
• BaseSettings::readBinary passes the index from accessor.find to field_infos[] without checking for the not-found sentinel value (i.e., -1), which may cause a std::vector out-of-bounds access. The issue was caught thanks to libcxx hardening. This probably happened during query plan deserialization when a newer server sends a setting unknown to an older server. The string-based read method already handles this correctly; readBinary was missing the same check. #97585 (Miсhael Stetsyuk).
• Fix incorrect query results for UNION ALL queries where one branch had a constant-false predicate — the branch would incorrectly read data instead of returning nothing. #97620 (Bharat Nallan).
• Fix IN (col) with a single column reference failing with UNSUPPORTED_METHOD error. #97646 (Alexey Milovidov).
• Fix logical error exception during GROUP BY ... WITH ROLLUP/CUBE when keys include LowCardinality(Nullable(...)) inside Nullable(Tuple(...)). #97647 (Alexey Milovidov).
• Fix AST formatting inconsistency for NOT (1, 1, 1) that could cause LOGICAL_ERROR in debug builds. #97653 (Alexey Milovidov).
• Fix keeper-converter exception when encountering empty ZooKeeper transaction log files. #97673 (Alexey Milovidov).

Build/Testing/Packaging Improvement

• ClickHouse can be built with clang-23 (master). #95578 (Alexey Milovidov).
• Fix force is_local to false when bind_host is configured and replace with integration test. Follow-up for #74741. #93109 #96018 (Zhigao Hong).
• Stress tests: fix stress and upgrade tests in CI. ignore no-{build} tags. add compatibility randomization. #94693 (Nikita Fomichev).
• Publish parser_memory_profiler binary from build. Tool can be used to analyze AST memory consumption. #95826 (Ilya Yatsishin).
• Add --symbolize flag for parser_memory_profiler tool that produces .heap.sym files with resolved symbols in results. #96477 (Ilya Yatsishin).
• Pin third-party Docker images in integration tests to specific versions. #96500 (Alexey Milovidov).
• Restore the possibility to link OpenSSL dynamically. This is not recommended and not used by any production builds, but the option still exists for enthusiasts on the Internet. #96506 (Govind R Nair).
• Reduce magic_enum range from [-100, 1000] to default [-128, 127] by using a per-type specialization for Coordination::OpNum, improving build time. #96632 (Alexey Milovidov).
• Remove unnecessary C++ templates from Function classes to reduce build times. #96646 (Alexey Milovidov).
• Move StorageSystemLicenses generation to configure time to improve build parallelism. #96697 (Alexey Milovidov).
• Parallelize license scanning. #96727 (Raúl Marín).
• Add stateless functional test for SSH protocol support. #96996 (Alexey Milovidov).
• Add Kafka 3.9.0 to the stateless functional test infrastructure, enabling direct testing of Kafka and Kafka2 table engines using ClickHouse Keeper as ZooKeeper. Six new stateless tests cover basic produce/consume, virtual columns, INSERT, multiple formats, broken message handling, and Keeper-based offset storage. #96997 (Alexey Milovidov).
• Add a CI workflow to build PGO+BOLT optimized clang toolchain. #96991 (Alexey Milovidov).
• Use the PGO-optimized LLVM/Clang build in CI, which should give 20..30% build speed improvement. #97031 (Alexey Milovidov).
• Replace math functions from glibc with llvm-libc implementations. #90151 (Konstantin Bogdanov).
• Update Boost from 1.83 to 1.90, fixing a devector assertion failure in debug builds. #97037 (Alexey Milovidov).
• Update postgres to REL_18_1. #95189 (Konstantin Bogdanov).
• Use libexpat 2.7.3. #95218 (Konstantin Bogdanov).
• Use OpenSSL 3.5.5. #95345 (Konstantin Bogdanov).
• Use simdjson v4.2.4. #97129 (Konstantin Bogdanov).
• Use libarchive 3.8.5. #97131 (Konstantin Bogdanov).
• Use fast_float v8.2.3. #97133 (Konstantin Bogdanov).
• Use abseil-cpp 20260107.1, s2geometry to v0.13.1. #97134 (Konstantin Bogdanov).
• Bump libxml2 to 2.15.1. #95574 (Robert Schulze).
• Upgraded 7 Tier-3 integration test Docker images from EOL or removed base images to current supported versions. #97314 (Rahul).
• Add TPC-DS benchmark queries. #97349 (Raufs Dunamalijevs).
• Replace individual x86 instruction-set cmake options (ENABLE_SSSE3, ENABLE_AVX2, NO_SSE3_OR_HIGHER, ARCH_NATIVE, etc.) with a single numeric X86_ARCH_LEVEL option (1/2/3/4), matching the standard x86-64 microarchitecture levels already used by the runtime dispatch system. #97354 (Raúl Marín).
• Avoid instantiating division_by_nullable=true template variants for non-division operations in FunctionBinaryArithmetic, reducing compilation time and binary size. #97496 (Raúl Marín).
• Reduce the include footprint of Exception.h by removing it from high-fan-out headers like typeid_cast.h, assert_cast.h, Context_fwd.h, IDataType.h, and various Column headers. #97497 (Raúl Marín).
• Always use bundled compiler-rt headers (sanitizer and XRay interfaces) instead of the host compiler's headers, and build compiler-rt libraries from source by default. #97499 (Raúl Marín).
• Avoid including boost/multiprecision headers in wide_integer_impl.h on platforms with adequate long double, improving build time. #96633 (Alexey Milovidov).
• Implement LLVM Code Coverage job and enable it initially for master branch. #90952 (Alexey Bakharew).
• Enable fast libcxx hardening for release builds. This is mostly needed for out-of-bounds checks. Given performance tests results, no noticeable performance impact is expected. #94757 (Miсhael Stetsyuk).

ClickHouse release 26.1, 2026-01-29. Presentation, Video

Backward Incompatible Change

• Fix inconsistent formatting caused by an incorrect substitution of aliases in the formatter. This closes #82833. This closes #82832. This closes #68296. This change is potentially backward incompatible: when the analyzer is disabled, certain CREATE VIEW queries with IN referencing an alias cannot be processed. To prevent the incompatibility, enable the analyzer (it is enabled by default since 24.3). #82838 (Alexey Milovidov).
• Codecs DEFLATE_QPL and ZSTD_QAT were removed. Users are advised to convert existing data compressed with DEFLATE_QPL or ZSTD_QAT to another codec before upgrade. Note that in order to use the codecs, settings enable_deflate_qpl_codec and enable_zstd_qat_codec had to be enabled. #92150 (Robert Schulze).
• Improve UDF debugging by enabling stderr capture in system.query_log.exception. Previously, UDF stderr was only logged to files and not exposed in query logs, making debugging impossible. Now stderr triggers exceptions by default and is fully accumulated (up to 1MB) before throwing, so complete Python tracebacks and error messages appear in system.query_log.exception for effective troubleshooting. #92209 (Xu Jia).
• Empty column list in JOIN USING () clause is now considered a syntax error. Previously it was supposed to be INVALID_JOIN_ON_EXPRESSION during query execution. In some cases such as joining with Join storage it led to LOGICAL_ERROR, close #82502. #92371 (Vladimir Cherkasov).
• Use partial match for SKIP REGEXP in JSON type by default. Closes #79250. #92847 (Pavel Kruglov).
• Revert "Allow INSERT into simple ALIAS columns" (Reverts ClickHouse/ClickHouse#84154). It does not work with custom formats, and is not guarded with a setting. #92849 (Azat Khuzhin).
• Setting to throw an error if a data lake catalog doesn't have access to object storage. #93606 (Konstantin Vedernikov).
• The Lazy database engine is removed and no longer available. Closes #91231. #93627 (Alexey Milovidov).
• Remove the transposed_with_wide_view mode of the metric_log - it is unusable due to a bug. It is no longer possible to define system.metric_log with this mode. This partially reverts #78412. #93867 (Alexey Milovidov).
• CPU scheduling for workloads is now preemptive by default. See cpu_slot_preemption server setting. #94060 (Sergei Trifonov).
• Escape index filenames to prevent broken parts. With this change ClickHouse will fail to load indices with non-ascii characters in their name created by previous versions. To handle it you can use the merge tree setting escape_index_filenames. #94079 (Raúl Marín).
• Format settings exact_rows_before_limit, rows_before_aggregation, cross_to_inner_join_rewrite, regexp_dict_allow_hyperscan, regexp_dict_flag_case_insensitive, regexp_dict_flag_dotall and dictionary_use_async_executor were changed to be regular (non-format) settings now. This is a purely internal change without user-visible side effects except in the (unlikely) case that you specified any of these settings in Iceberg or DeltaLake or Kafka or S3 or S3Queue or Azure or Hive or RabbitMQ or Set or FileLog or NATS table engine definitions. In these cases, these settings were previously ignored, now such definitions throw an error. #94106 (Robert Schulze).
• The joinGet/joinGetOrNull functions now enforce SELECT privileges on the underlying Join table. After this change, executing joinGet('db.table', 'column', key) requires the user to have SELECT privilege on both the key columns defined in the Join table and the attribute column being retrieved. Queries lacking these privileges will fail with ACCESS_DENIED. To migrate, grant the necessary permissions using GRANT SELECT ON db.join_table TO user for full table access, or GRANT SELECT(key_col, attr_col) ON db.join_table TO user for column-level access. This change affects all users and applications relying on joinGet/joinGetOrNull where explicit SELECT grants were not previously configured. #94307 (Vladimir Cherkasov).
• Check SHOW COLUMNS for CREATE TABLE ... AS ... queries. Previously, it checked SHOW TABLES, which is an incorrect grant for this type of permission check. #94556 (pufit).
• Make the Hash output format independent of block sizes. #94503 (Alexey Milovidov). Note that this changes the output hash values compared to previous versions.

New Feature

• HTTP API and embedded Web UI for ClickHouse Keeper. #78181 (pufit and speeedmaster).
• Async insert deduplication now works with dependent materialized views. When collision by block_id occurs, the original block is filtered to remove rows associated with the block_id, and the remaining rows are transformed with all relevant materialized views select queries, this rebuilds original block without conflicting rows. #89140 (Sema Checherinda). It is allowed to use deduplication with async inserts when materialized views are involved. #93957 (Sema Checherinda).
• Introduced a new syntax and framework to simplify and extend projection index feature. This follows up https://github.com/ClickHouse/ClickHouse/pull/81021. #91844 (Amos Bird).
• Add text index support for Array columns. #89895 (Jimmy Aguilar Mena).
• Enable use_variant_as_common_type by default, which lets you use incompatible types inside an Array, in UNION queries, and in branches of if/multiIf/case. #90677 (Alexey Milovidov).
• New system table zookeeper_info. Implements #88014. #90809 (Smita Kulkarni).
• Support the Variant type in all functions. #90900 (Bharat Nallan).
• Adds a ClickHouse_Info metric to the Prometheus /metrics endpoint containing mainly version information so it's possible to build charts tracking detailed version information over time. #91125 (Christoph Wurm).
• Introduce a new four letter rcfg command for keeper which allows to change cluster configuration. This command provides broader possibilities for configuration changes than standard reconfigure request. Command takes json string as an argument. The whole set of bytes sent to TCP interface should look like this: rcfg{json_string_length_big_endian}{json_string}. Some examples of command may look like this: {"preconditions": {"leaders": [1, 2], "members": [1, 2, 3, 4, 5]}, "actions": [{"transfer_leadership": [3]}, {"remove_members": [1, 2]}, {"set_priority": [{"id": 4, "priority": 100}, {"id": 5, "priority": 100}]}, {"transfer_leadership": [4, 5]}, {"set_priority": [{"id": 3, "priority": 0}]}]}. #91354 (alesapin).
• Add function reverseBySeparator which reverses the order of substrings in a string separated by a specified separator. Close #91463. #91780 (Xuewei Wang).
• Adds new setting max_insert_block_size_bytes which control the formation of inserted blocks in finer detail. #92833 (Kirill Kopnev).
• It is possible to execute DDL queries with ON CLUSTER clause for a Replicated database if the ignore_on_cluster_for_replicated_database setting is enabled. In this case, the cluster name will be ignored. #92872 (Kirill).
• Implement mergeTreeAnalyzeIndexes function. #92954 (Azat Khuzhin).
• Add new setting use_primary_key. Set it to false to disable granule pruning based on the primary key. #93319 (Nihal Z. Miaji).
• Add icebergLocalCluster table function. #93323 (Anton Ivashkin).
• Added cosineDistanceTransposed function that approximates the cosine distance between two points. #93621 (Raufs Dunamalijevs).
• Add files column to system.parts table that shows the number of files in each data part. #94337 (Match).
• Adds a max-min fair scheduler for concurrency control. Provides better fairness under high oversubscription, where many queries compete for limited CPU slots. Short-running queries are not penalized by long-running queries that have accumulated more slots over time. Enabled by the concurrent_threads_scheduler server setting max_min_fair value. #94732 (Sergei Trifonov).
• Added the ability for ClickHouse client to override TLS SNI when connecting to the server. #89761 (Matt Klein).
• Support temporary tables in joinGet function calls. #92973 (Eduard Karacharov).
• Support deletion vectors in DeltaLake table engine. #93852 (Kseniia Sumarokova).
• Support deletion vectors for deltaLakeCluster. #94365 (Kseniia Sumarokova).
• Google cloud storage support for data lakes. #93866 (Konstantin Vedernikov).

Experimental Feature

• Move QBit from Experimental to Beta. #93816 (Raufs Dunamalijevs).
• Add support for Nullable(Tuple). Set allow_experimental_nullable_tuple_type = 1 to enable it. #89643 (Nihal Z. Miaji).
• Support Paimon REST catalog, continuing from https://github.com/ClickHouse/ClickHouse/pull/84423. #92011 (JIaQi Tang).

Performance Improvement

• Setting use_skip_indexes_on_data_read is now enabled by default. This setting allows filtering in a streaming fashion, at the same time as reading, improving query performance and startup time. #93407 (Shankar Iyer).
• Improve performance of DISTINCT on LowCardinality columns. Closes #5917. #91639 (Nihal Z. Miaji).
• Optimize distinctJSONPaths aggregate function so it reads only JSON paths from data parts and not the whole JSON column. #92196 (Pavel Kruglov).
• More filters pushed down JOINs. #85556 (Nikita Taranov).
• Support more cases for push down from join ON condition when the filter uses inputs only from one side. Support ANY, SEMI, ANTI joins. #92584 (Dmitry Novik).
• Allow using equivalent sets to push down filters for SEMI JOIN. Closes #85239. #92837 (Dmitry Novik).
• Skip reading left side of hash join when right side is empty. Previously we were reading left side until first non-empty block, which might do a lot of work in case when there is heavy filtering or aggregation. #94062 (Alexander Gololobov).
• Using the "fastrange" (Daniel Lemire) method for partitioning data inside the query pipeline. This could improve parallel sorting and JOINs. #93080 (Alexey Milovidov).
• Improve performance of window functions when PARTITION BY matches or is a prefix of the sorting key. #87299 (Nikita Taranov).
• Outer filter is pushed down into views which allows applying PREWHERE on local and remote nodes. Resolves #88189. #88316 (Igor Nikonov).
• Implement JIT compilations for more functions. Closes #73509. #88770 (Alexey Milovidov with Taiyang Li).
• If a skip index used in a FINAL query is on a column that is part of the primary key, the additional step to check for primary key intersection in other parts is unnecessary and now not performed. Resolves #85897. #93899 (Shankar Iyer).
• Optimize performance and memory usage for fractional LIMIT and OFFSET. #91167 (Ahmed Gouda).
• Fix using of faster random read logic for Parquet Reader V3 prefetcher. Closes #90890. #91435 (Arsen Muk).
• Improve performance of icebergCluster. Closes #91462. #91537 (Yang Jiang).
• Don't filter by virtual columns on constant filters. #91588 (c-end).
• Reduce INSERT/merges memory usage with wide parts for very wide tables by enabling adaptive write buffers. Add support of adaptive write buffers for encrypted disks. #92250 (Azat Khuzhin).
• Improved performance of full text search with text index and sparseGrams tokenizer by reducing the number of searched tokens in the index. #93078 (Anton Popov).
• Function isValidASCII was optimized for positive outcomes, i.e. all-ASCII input values. #93347 (Robert Schulze).
• The read-in-order optimization now recognizes when ORDER BY columns are constant due to WHERE conditions, enabling efficient reverse-order reads. This benefits multi-tenant queries like WHERE tenant='42' ORDER BY tenant, event_time DESC which can now use InReverseOrder instead of requiring a full sort.". #94103 (matanper).
• Introduce Enum AST specialized class to store value parameters in (string, integer) pairs instead of ASTLiteral children to optimize memory consumption. #94178 (Ilya Yatsishin).
• Distributed index analysis on multiple replicas. Beneficial for shared storage and huge amount of data in cluster. This is applicable for SharedMergeTree (ClickHouse Cloud) and could be applicable for other types of MergeTree tables on a shared storage. #86786 (Azat Khuzhin).
• Reduce overhead of join runtime filters by disabling them in the following cases: - too many bits are set in the bloom filter - too few rows are filtered out at runtime. #91578 (Alexander Gololobov).
• Use an in-memory buffer for correlated subqueries input to avoid evaluating it multiple times. Part of #79890. #91205 (Dmitry Novik).
• Allow all replicas to steal orphaned ranges in parallel replicas reading. This improves load balancing and reduces long-tail latency. #91374 (zoomxi).
• External aggregation/sorting/join now respects query setting temporary_files_codec in all contexts. Fixed missing profile events for grace hash join. #92388 (Vladimir Cherkasov).
• Make query memory usage detection for spilling to disk during aggregation/sorting more robust. #92500 (Azat Khuzhin).
• Estimate total rows count and NDV (number of distinct values) statistics of aggregation key columns. #92812 (Alexander Gololobov).
• Optimize postings list compression with simdcomp. #92871 (Peng Jian).
• Refactor S3Queue Ordered mode processing with buckets. This should also improve performance, reducing the number of keeper requests. #92889 (Kseniia Sumarokova).
• Functions mapContainsKeyLike and mapContainsValueLike can now leverage a text index on mapKeys() or mapValues(), respectively. #93049 (Michael Jarrett).
• Reduce memory usage on non-Linux systems (enable immediate purging of jemalloc dirty pages). #93360 (Eduard Karacharov).
• Force purging of jemalloc arenas in case the ratio of dirty pages size to max_server_memory_usage exceeds memory_worker_purge_dirty_pages_threshold_ratio. #93500 (Eduard Karacharov).
• Reduce memory usage for AST. #93601 (Nikolai Kochetov).
• In some cases we've seen ClickHouse doesn't respect a memory limit when reading from a table. This behaviour is fixed. #93715 (Nikita Mikhaylov).
• Enable CHECK_STAT and TRY_REMOVE Keeper extension by default. #93886 (Mikhail Artemenko).
• Parse lower and upper bounds of file names corresponding to position deletes from Iceberg manifest file entries for better selection of corresponding data files. #93980 (Daniil Ivanik).
• Add two more settings to control maximum number of dynamic subcolumns in JSON column. First is MergeTree setting merge_max_dynamic_subcolumns_in_compact_part (similar to already added merge_max_dynamic_subcolumns_in_wide_part) that limits number of dynamic subcolumns created during merge into a Compact part. Second is query level setting max_dynamic_subcolumns_in_json_type_parsing that limits number of dynamic subcolumns created during parsing of JSON data, it will allow to specify the limit on insert. #94184 (Pavel Kruglov).
• Slightly optimize squashing of JSON columns for some cases. #94247 (Pavel Kruglov).
• Lower the thread pool queue sizes based on the production experience. Add an explicit memory consumption check before reading any data from the MergeTree. #94692 (Nikita Mikhaylov).
• Make sure the scheduler would prefer MemoryWorker thread under the CPU starvation, because it protects ClickHouse process from an existential threat. #94864 (Nikita Mikhaylov).
• Run purging of jemalloc dirty pages in a different thread from main thread of MemoryWorker. If purging is slow, it could delay updates of RSS usage which could lead to out of memory kills of the process. Introduce new config memory_worker_purge_total_memory_threshold_ratio to start purging dirty pages based on ratio of total memory usage. #94902 (Antonio Andelic).

Improvement

• system.blob_storage_log is now available for Azure Blob Storage. #93105 (Alexey Milovidov).
• Implement blob_storage_log for Local and HDFS. Fix an error when S3Queue used something other than the disk name for logging in blob_storage_log. Add error_code column to blob_storage_log. Split the test configuration file to simplify local testing. #93106 (Alexey Milovidov).
• clickhouse-client and clickhouse-local will highlight digit groups (thousands, millions, etc.) inside numeric literals while typing. This closes #93100. #93108 (Alexey Milovidov).
• Adds support in clickhouse-client for command-line arguments with a space surrounding the equals sign. Closes #93077. #93174 (Cole Smith).
• With <interactive_history_legacy_keymap>true</interactive_history_legacy_keymap>, the CLI client can now fall back to Ctrl-R for regular search like before, while Ctrl-T does fuzzy search. #87785 (Larry Snizek).
• The statement to clear caches SYSTEM DROP [...] CACHE gave the false impression that the statement disables the cache. ClickHouse now supports statement SYSTEM CLEAR [...] CACHE which is more obvious. The old syntax remains available. #93727 (Pranav Tiwari).
• Support multiple columns as primary key in EmbeddedRocksDB. Closes #32819. #33917 (usurai).
• It is now possible to use non-constant IN for scalars (queries like val1 NOT IN if(cond, val2, val3)). #93495 (Yarik Briukhovetskyi).
• Prevent x-amz-server-side-encryption headers from being propagated to HeadObject, UploadPart & CompleteMultipartUpload S3 requests as they're not supported. #64577 (Francisco J. Jurado Moreno).
• Tracking hive partitioning for ordered mode in S3Queue. Resolves #71161. #81040 (Anton Ivashkin).
• Optimize space reservation in filesystem cache. FileCache::collectCandidatesForEviction will be executed without unique lock. #82764 (Kseniia Sumarokova).
• Support composite rotation strategy (size + time) for server log. #87620 (Jianmei Zhang).
• CLI client can now specify <warnings>false</warnings> instead of the command line --no-warnings. #87783 (Larry Snizek).
• Add support for the avg aggregate function with Date, DateTime and Time values as arguments. Closes #82267. #87845 (Yarik Briukhovetskyi).
• The optimization use_join_disjunctions_push_down is enabled by default. #89313 (Alexey Milovidov).
• Support more table engines and data source kinds in the correlated subqueries. Closes #80775. #90175 (Dmitry Novik).
• If the schema of parameterized view is specified explicitly, it is shown. Close #88875, #81385. #90220 (Grigorii Sokolik).
• Correctly handle the gap in Keeper log entries if logs are before the last committed index. #90403 (Antonio Andelic).
• Improve min_free_disk_bytes_to_perform_insert setting to work correctly with JBOD volumes. #90878 (Aleksandr Musorin).
• Make it possible to specify storage_class_name setting in named collections for S3 table engine and s3 table function. #91926 (János Benjamin Antal).
• Support inserting auxiliary zookeeper by system.zookeeper. #92092 (RinChanNOW).
• Add new metrics for the keeper: KeeperChangelogWrittenBytes, KeeperChangelogFileSyncMicroseconds, KeeperSnapshotWrittenBytes and KeeperSnapshotFileSyncMicroseconds profile events as well as KeeperBatchSizeElements and KeeperBatchSizeBytes histogram metrics. #92149 (Miсhael Stetsyuk).
• Add a new setting, trace_profile_events_list, which limits tracing with trace_profile_event to the specified list of event names. This allows more precise data collection on large workloads. #92298 (Alexey Milovidov).
• Support SYSTEM NOTIFY FAILPOINT for pausable failpoints. - Support SYSTEM WAIT FAILPOINT fp PAUSE/RESUME. #92368 (Shaohua Wang).
• Add creation (implicit/explicit) column to system.data_skipping_indices. #92378 (Raúl Marín).
• Allow passing the description of columns for YTsaurus dyn tables to the dictionary source. #92391 (MikhailBurdukov).
• In #63985, we made it possible to specify all the parameters needed for TLS configuration on a per-port basis (see composable protocols), so we don't have to rely on global TLS config. However, the implementation still implicitly requires a global openSSL.server config section to exist, which conflicts with setups where different TLS configurations are needed for different ports. For example, in keeper-in-server deployments, we need separate TLS configs for inter-keeper communication and clickhouse client connections. #92457 (Miсhael Stetsyuk).
• Introduce a new setting input_format_binary_max_type_complexity that limits the total number of type nodes that can be decoded in binary format to prevent malicious payloads. #92519 (Raufs Dunamalijevs).
• Reflect running tasks in system.background_schedule_pool{,_log}. Add documentation. #92587 (Azat Khuzhin).
• Execute current query in Ctrl+R search in client if no history match found. #92749 (Azat Khuzhin).
• Support EXPLAIN indices = 1 as an alias for EXPLAIN indexes = 1. Closes #92483. #92774 (Pranav Tiwari).
• Parquet reader now allows reading Tuple or Map columns as JSON: select x from file(f.parquet, auto, 'x JSON') works even if the type of column x in f.parquet is tuple or map. #92864 (Michael Kolupaev).
• Support empty tuples in parquet reader. #92868 (Michael Kolupaev).
• Fallback to read-write copy for Azure Blob Storage when native copy fails with BadRequest (e.g. invalid block list). Previously this was only done for Unauthorized error which was seen while copying blob to different storage accounts. But we also sometimes see "The specified block list is invalid" error. So now updated the condition to fallback to read & write for all native copy fails. #92888 (Smita Kulkarni).
• Fix EC2 metadata endpoint throttling when running many concurrent S3 queries with EC2 instance profile credentials. Previously, each query created its own AWSInstanceProfileCredentialsProvider, causing concurrent requests to the EC2 metadata service which could result in timeouts and HTTP response code: 403 errors. Now the credentials provider is cached and shared across all queries. #92891 (Sav).
• Rework insert_select_deduplicate setting to add an ability to keep backward compatibility. #92951 (Sema Checherinda).
• Log background tasks that are slower than average (background_schedule_pool_log.duration_threshold_milliseconds=30) to avoid excessive tasks logging. #92965 (Azat Khuzhin).
• In previous versions, some of C++ function names were displayed incorrectly ("mangled") in the system.trace_log and system.symbols, and the demangle function didn't process them well. Closes #93074. #93075 (Alexey Milovidov).
• Introduced the backup_data_from_refreshable_materialized_view_targets backup setting to skip back up of refreshable materialized views. RMVs with APPEND refresh strategy which are always backed up. #93076 (Julia Kartseva). #93658 (Julia Kartseva)
• Use minimal debug info instead of no debug info for heavy translation units, such as functions. #93079 (Alexey Milovidov).
• Added MinIO compatibility support to AWS S3 C++ SDK by implementing error code mapping for MinIO-specific errors. This change allows ClickHouse to properly handle and retry MinIO server errors when using MinIO deployments instead of AWS S3, improving reliability for users running object storage on self-hosted MinIO clusters. #93082 (XiaoBinMu).
• Write symbolized jemalloc profiles (eliminating the need for a binary during heap profile generation). #93099 (Azat Khuzhin).
• Resurrect clickhouse git-import tool - it was broken on large and invalid commits. See https://presentations.clickhouse.com/2020-matemarketing/. #93202 (Alexey Milovidov).
• Don't show passwords from URL storage in query log. #93245 (Konstantin Vedernikov).
• Support Geometry type for flipCoordinates. #93303 (Bharat Nallan).
• Improve the UX of SYSTEM INSTRUMENT ADD/REMOVE: use String literals for function names, patch all functions that match and allow using function_name in REMOVE. #93345 (Pablo Marcos).
• Add a new setting materialize_statistics_on_merge which enables/disables materializing statistics during merge. The default value is 1. #93379 (Han Fei).
• ClickHouse can now parse SELECT without parentheses around DESCRIBE SELECT queries. Closes #58382. #93429 (Yarik Briukhovetskyi).
• Add randomization of cache correctness checks under probability. #93439 (Kseniia Sumarokova).
• Add setting type_json_allow_duplicated_key_with_literal_and_nested_object to allow duplicated paths in JSON where one is a literal and another is a nested object, e.g. {"a" : 42, "a" : {"b" : 42}}. Some data could be created before this restriction on duplicated paths was added in https://github.com/ClickHouse/ClickHouse/pull/79317 and further manipulation with this data can lead to errors now. With this setting, such old data cane still be used with no errors. #93604 (Pavel Kruglov).
• Don't print values of simple types on separate lines in Pretty JSON. #93836 (Pavel Kruglov).
• When there are many alter table ... modify setting ... statements, it's possible not to acquire lock for 5 seconds. Better to return timeout than logical error. #93856 (Han Fei).
• Prevent excessive output on a syntax error. Before this change, it output the whole SQL script, which could contain a lot of queries. #93876 (Alexey Milovidov).
• Do proper byte size calculation of the check request with stats in Keeper. #93907 (Mikhail Artemenko).
• Added use_hash_table_stats_for_join_reordering setting to control whether runtime hash table size statistics are used for join reordering. This setting is enabled by default, preserving the existing behavior of collect_hash_table_stats_during_joins. #93912 (Vladimir Cherkasov).
• Users can now partially view nested global server settings in the system.server_settings table (e.g. logger.level). This only covers settings with a fixed structure (no lists, enumerations, repetitions etc.). #94001 (Hechem Selmi).
• QBit can now be compared for equality. #94078 (Raufs Dunamalijevs).
• When Keeper detects broken snapshot or inconsistent changelogs, throw exception instead of manually aborting or cleaning up files automatically. This should lead to a safer behaviour of Keeper relying on manual intervention. #94168 (Antonio Andelic).
• Fix leaving possible leftovers in case of CREATE TABLE fails. #94174 (Azat Khuzhin).
• Fix uninitialized memory access (a bug in OpenSSL) when password protected TLS key is used. #94182 (Konstantin Bogdanov).
• Bump chdig to v26.1.1. #94290 (Azat Khuzhin).
• Support more generic partitioning for S3Queue ordered mode. #94321 (Bharat Nallan).
• Added alias use_statistics for setting allow_statistics_optimize. This is more consistent with existing settings use_primary_key and use_skip_indexes. #94366 (Robert Schulze).
• Enabled setting input_format_numbers_enum_on_conversion_error for conversion from Numbers to Enums to check whether the element exists. #94384 (Elmi Ahmadov).
• In S3(Azure)Queue ordered mode clean up failed nodes by tracking limits (before that was done only in Unordered mode for both failed and processed, so now this will also be done for Ordered but only for failed nodes). #94412 (Kseniia Sumarokova).
• Enable access management for default user in clickhouse-local. The default user in clickhouse-local was missing the access_management privilege, which caused operations like DROP ROW POLICY IF EXISTS to fail with ACCESS_DENIED error, even though the user should be unrestricted. #94501 (Alexey Milovidov).
• Enable named collection for YTsaurus dictionaries and tables. #94582 (MikhailBurdukov).
• Add support for SQL-defined named collections in BACKUP/RESTORE for S3 and Azure Blob Storage. Closes #94604. #94605 (Pablo Marcos).
• Support bucketing based on partition key for S3Queue in ordered mode. #94698 (Bharat Nallan).
• Add an asynchronous metric with the longest running merge elapsed time. #94825 (Raúl Marín).
• Add belonging file check before apply position delete using IcebergBitmapPositionDeleteTransform. #94897 (Yang Jiang).
• Now view_duration_ms shows the time when group was active, not the sum of the threads duration in it. #94966 (Sema Checherinda).
• Remove limit of the max number of search tokens in hasAnyTokens and hasAllTokens functions which was limited to 64. Example: SELECT count() FROM table WHERE hasAllTokens(text, ['token_1', 'token_2', [...], 'token_65']]); The query would result in a BAD_ARGUMENTS error because there are 65 search tokens. With this PR, the limit has been removed completely and the same query would run without an error. #95152 (Elmi Ahmadov).
• Add a setting input_format_numbers_enum_on_conversion_error for conversion from Numbers to Enums to check whether the element exists. Closes: #56144. #56240 (Nikolay Degterinsky).
• Share format parser resources between data file and position delete file reading in Iceberg tables to reduce memory allocations. #94701 (Yang Jiang).

Bug Fix (user-visible misbehavior in an official stable release)

• Fixes a bug where predefined query handlers would have trailing whitespace interpreted as data during inserts. #83604 (Fabian Ponce).
• Fix INCOMPATIBLE_TYPE_OF_JOIN error for Join storage and outer to inner join optimization applied. Resolves #80794. #84292 (Vladimir Cherkasov).
• Fix exception "Invalid number of rows in Chunk" when using hash join with allow_experimental_join_right_table_sorting enabled. #86440 (yanglongwei).
• Always replace file names to hash in MergeTree if filesystem is case insensitive. Previously on systems with case insensitive filesystem (like MacOS) it could lead to data corruption when several column/subcolumn names differs only in the case. #86559 (Pavel Kruglov).
• Add a full permissions check on the create stage for the underlying query inside a materialized view. #89180 (pufit).
• Fixed crash in icebergHash function on constant argument. #90335 (Michael Kolupaev).
• Fix logical error when mutation without transaction mutates parts in an active transaction, which is rolled back finally. #90469 (Shaohua Wang).
• Update system.warnings correctly after an ordinary database was converted to an atomic database. #90473 (sdk2).
• Fixes an assertion when reading from Parquet file, and part of a prewhere expression is used elsewhere in the query. #90635 (Max Kainov).
• Fix crash in a single-node cluster when reading from Iceberg in split-by-buckets mode. This closes #90913. #91553 (Konstantin Vedernikov).
• Fix possible logical error in Log engine during subcolumns reading. Closes #91710. #91711 (Pavel Kruglov).
• Fix Logical error: 'Storage does not support transaction' during ATTACH AS REPLICATED. #91772 (Shaohua Wang).
• Fix for runtime filters working incorrectly when LEFT ANTI JOIN has extra post-condition. #91824 (Alexander Gololobov).
• Fixes an error where we have a null-safe comparison involving the Nothing type. Closes #91834. Closes #84870. Closes #91821. #91884 (Yarik Briukhovetskyi).
• Fix DELTA_BYTE_ARRAY decoding bugs in native Parquet reader affecting highly repetitive string data. #91929 (Daniel Muino).
• Cache schema only for the file it was inferred from in globs instead of all files during schema inference. Closes #91745. #92006 (Pavel Kruglov).
• Fix the Couldn't pack tar archive: Failed to write all bytes error caused by an incorrect archive entry size header. Fixes #89075. #92122 (Julia Kartseva).
• Release request stream in insert select to prevent closing http connection. #92175 (Sema Checherinda).
• Fix logical error for queries with multiple JOINs with USING clause and join_use_nulls. #92251 (Vladimir Cherkasov).
• Fix logical error while join reordering with join_use_nulls, close https://github.com/clickhouse/clickhouse/issues/90795. #92289 (Vladimir Cherkasov).
• Fix inconsistent AST formatting of arrayElement with negate literal. Closes #92288 Closes #92212 Closes #91832 Closes #91789 Closes #91735 Closes #88495 Closes #92386. #92293 (Pavel Kruglov).
• Fix a possible crash with join_on_disk_max_files_to_merge setting. #92335 (Bharat Nallan).
• Related issue #https://github.com/ClickHouse/support-escalation/issues/6365. #92339 (Tuan Pham Anh).
• Fix missing access check in SYSTEM SYNC FILE CACHE. Closes #92101. #92372 (Kseniia Sumarokova).
• Fix count_distinct_optimization pass over window functions and over multiple arguments. #92376 (Raúl Marín).
• Fix "Cannot write to finalized buffer" error when using certain aggregate functions with window functions. Closes #91415. #92395 (Jimmy Aguilar Mena).
• Fix logical error with CREATE TABLE ... AS urlCluster() and database engine Replicated. Closes #92216. #92418 (Kseniia Sumarokova).
• Inherit source part serialization info settings during mutation in MergeTree. It fixes possible incorrect result of the query over mutated part after changes in data types serialization. #92419 (Pavel Kruglov).
• Fix possible conflict in column and subcolumn with the same name leading in using wrong serialization and query failures. Closes #90219. Closes #85161. #92453 (Pavel Kruglov).
• Fix a LOGICAL_ERRORs that caused by not wanted modification of query plan when converting outer join to inner join. Also relax the requirements of optimization to be able to apply it in cases when injective functions are applied to the aggregating keys during joins. #92503 (János Benjamin Antal).
• Fix possible error SIZES_OF_COLUMNS_DOESNT_MATCH during sorting of emty tuple column. Closes #92422. #92520 (Pavel Kruglov).
• Check for incompatible typed paths in JSON type. Closes #91577. #92539 (Pavel Kruglov).
• Fix deadlock for SHOW CREATE DATABASE for Backup database. #92541 (Azat Khuzhin).
• Use proper error code when validating hypothesis index. #92559 (Raúl Marín).
• Fix dynamic subcolumns resolution in column aliases in analyzer. Previously dynamic subcolumn in column alias was wrapped in getSubcolumn and in some cases could be not resolved at all. Closes #91434. #92583 (Pavel Kruglov).
• Prevent crash in tokens() with null second argument. #92586 (Raúl Marín).
• Fix potential crash caused by in place mutation of underlying const PREWHERE columns. This could've happened at column shrinking (IColumn::shrinkToFit) or filtering (IColumn::filter), which could've triggered concurrently from several threads. #92588 (Arsen Muk).
• Creating and materializing text indexes on tables containing large parts (over 4,294,967,295 rows) is temporarily disabled. This limitation prevents incorrect query results, as the current index implementation does not yet support such large parts. #92644 (Anton Popov).
• Fixes a logical error Too large size (A) passed to allocator while executing JOINs. Closes #92043. #92667 (Yarik Briukhovetskyi).
• Remove a bug that ngrambf_v1 indexes with ngram length (1st parameter) > 8 would throw an exception. #92672 (Robert Schulze).
• Fix uncaught exception during background named collections reload when zookeeper storage is used. Closes https://github.com/ClickHouse/clickhouse-private/issues/44180. #92717 (Kseniia Sumarokova).
• Reworks incorrect logic in access grant checks for wildcard grants. The previous attempt https://github.com/ClickHouse/ClickHouse/pull/90928 addressed a critical vulnerability but ended up being too restrictive, resulting in some wildcard GRANT statements failing due to unrelated revokes. #92725 (pufit).
• Fix bug in data skipping logic when not match(...) is used in WHERE causing incorrect results. Closes #92492. #92726 (Nihal Z. Miaji).
• Do not attempt to delete temporary directories at startup if a MergeTree table is created over a read-only disk. #92748 (Alexey Milovidov).
• Fix "Cannot add action to empty ExpressionActionsChain" for ALTER TABLE REWRITE PARTS (v2). #92754 (Azat Khuzhin).
• Avoid crash due to reading from a disconnected Connection. #92807 (Raufs Dunamalijevs).
• Fix logical error Failed to set file processing within 100 retries in storgae S3Queue in Ordered mode. It is now replaced with a warning. This error could happen before 25.10 version if keeper session expired, however it will still be a warning in 25.10+ versions, as it is still theoretically possible to get this error in case of high processing concurrency in Ordered mode. #92814 (Kseniia Sumarokova).
• Previously, some queries that used PK sharding with a false condition were failing. Now they're not. Needed for https://github.com/ClickHouse/ClickHouse/pull/89313. #92815 (Yarik Briukhovetskyi).
• Fixed calculation of uncompressed sizes of text indexes in the system.parts table. #92832 (Anton Popov).
• Fixed usage of primary index in lightweight updates that have an IN clause with subqueries in the predicate of the WHERE clause. #92838 (Anton Popov).
• Fix creating type hint for path 'skip' in JSON. Closes #92731. #92842 (Pavel Kruglov).
• In the S3 table engine, we should avoid caching the partition key if there are non-deterministic functions. #92844 (Miсhael Stetsyuk).
• Fix possible error FILE_DOESNT_EXIST after mutation of a sparse column with ratio_of_defaults_for_sparse_serialization=0.0. Closes #92633. #92860 (Pavel Kruglov).
• Fix parquet schema inference in the old parquet reader (not used by default) when a JSON column comes after a Tupe column. Fix the old parquet reader (not used by default) failing on empty tuples. #92867 (Michael Kolupaev).
• Fix logical error with multiple joins on constant condition and join_use_nulls, close #92640. #92892 (Vladimir Cherkasov).
• Fix possible error NOT_FOUND_COLUMN_IN_BLOCK during insert into a table with subcolumn in partition expression. Closes #93210. Closes #83406. #92905 (Pavel Kruglov).
• Fix error NO_SUCH_COLUMN_IN_TABLE in Merge engine over tables with aliases. Closes #88665. #92910 (Pavel Kruglov).
• Fix NULL != NULL case for full_sorting_join on LowCardinality(Nullable(T)) column. #92924 (Vladimir Cherkasov).
• Fixed several crashes during merges of text indexes in MergeTree tables. #92925 (Anton Popov).
• Restore LowCardinality wrappers on SET expression results if needed during TTL aggregation to prevent exceptions during table optimization. #92971 (Seva Potapov).
• Fix logical error during index analysis when empty array is used in has function. Closes #92906. #92995 (Nihal Z. Miaji).
• Fix possible hung on terminating background schedule pool (may lead to server hungs on shutdown). #93008 (Azat Khuzhin).
• Fix possible error FILE_DOESNT_EXIST after sparse column mutation when setting ratio_of_defaults_for_sparse_serialization was changed to 1.0 via alter. #93016 (Pavel Kruglov).
• Fix bug in data skipping logic when not materialize(...) or not CAST(...) is used in WHERE causing incorrect results. Closes #88536. #93017 (Nihal Z. Miaji).
• Fix possible usage of outdated parts due to TOCTOU race for shared parts. #93022 (Azat Khuzhin).
• Fix crash when deserialising malformed groupConcat aggregate state with out-of-bounds offsets. #93028 (Raufs Dunamalijevs).
• Fix leaving connection in a broken state after preliminary cancellation distributed queries. #93029 (Azat Khuzhin).
• Fix join results when the right-side join key is a sparse column. This closes #92920. I can only reproduce the bug with set compatibility='23.3'. Not sure if it should be backported. #93038 (Amos Bird).
• Fix possible Cannot finalize buffer after cancellation in estimateCompressionRatio(). Fixes: #87380. #93068 (Azat Khuzhin).
• Fixed merges of text indexes built on top of the complex expressions (such as concat(col1, col2)). #93073 (Anton Popov).
• Fix applying projection when filter contains subcolumns. Closes #92882. #93141 (Pavel Kruglov).
• Fix logical error in some cases triggered when join runtime filters are added to query plan. It was caused by incorrectly returning duplicated const columns from one of join sides. #93144 (Alexander Gololobov).
• Special function __applyFilter used by join runtime filters was returning ILLEGAL_TYPE_OF_ARGUMENT in some valid cases. #93187 (Alexander Gololobov).
• Prevent different interpolated columns from collapse into the same column in a block when interpolated columns are effectively aliases of the same column. #93197 (Yakov Olkhovskiy).
• Do not add runtime filter when joining with already filled right table. #93211 (Alexander Gololobov).
• Fix keeper persistent watches cleanup after dead session. This closes #92480. #93213 (Konstantin Vedernikov).
• Fix order by tuple in iceberg. This closes #92977. #93225 (Konstantin Vedernikov).
• Fix bug with S3Queue setting s3queue_migrate_old_metadata_to_buckets. Closes #93392, #93196, #81739. #93232 (Kseniia Sumarokova).
• Remove unused columns when the projection is rebuilt during the merge. It reduces memory usage and creates fewer temporary parts. #93233 (Nikolai Kochetov).
• Fix unused columns removal from subqueries in the presence of a scalar correlated subquery. Before the fix column could have been removed if it was used only in the correlated subquery, and the query would fail with NOT_FOUND_COLUMN_IN_BLOCK error. #93273 (Dmitry Novik).
• Fix possible missing subcolumn in MV during alter of source table. Closes #93231. #93276 (Pavel Kruglov).
• Fix the Merge table engine query planning with the analyzer that could throw ILLEGAL_COLUMN for hostName() when merging local and remote/Distributed tables. Closes #92059. #93286 (Jinlin).
• Fixes a case where NOT IN with non-constant array arguments was returning the wrong value + Support for non-constant Array functions. Closes #14980. #93314 (Yarik Briukhovetskyi).
• Fix Not found column for use_top_k_dynamic_filtering optimization. Fixes #93186. #93316 (Nikolai Kochetov).
• Fixed rebuilding of text indexes created on top of subcolumns. #93326 (Anton Popov).
• Fixed handling of empty array as a second argument in hasAllTokens and hasAnyTokens functions. #93328 (Anton Popov).
• Fix logical error when runtime filters are used in a query with totals for right side table. #93330 (Alexander Gololobov).
• The server no longer crashes if function tokens is called with non-const tokenizer parameters (the 2th, 3rd, 4th parameter), e.g., SELECT tokens(NULL, 1, materialize(1)). #93383 (Robert Schulze).
• Fixed integer overflow vulnerability in groupConcat state deserialisation that could cause memory safety issues with crafted aggregate states. #93426 (Raufs Dunamalijevs).
• Fixed text index analysis on array columns when the index contains no tokens (all arrays are empty or all tokens are skipped by the tokenizer). #93457 (Anton Popov).
• Avoids oauth login in ClickHouse Client when username/password are within the connection string. #93459 (Krishna Mannem).
• Fix Azure ADLS Gen2 vended credentials support in DataLakeCatalog - parse adls.sas-token.* keys from Iceberg REST catalogs and fix ABFSS URL parsing. #93477 (Karun Anantharaman).
• Fix GLOBAL IN support with analyzer (previously set was created on the remote node again). #93507 (Azat Khuzhin).
• Fix extracting subcolumn during deserialization directly into Sparse columns. #93512 (Pavel Kruglov).
• Fixed direct reading from text index with duplicate search queries. #93516 (Anton Popov).
• Fix for NOT_FOUND_COLUMN_IN_BLOCK error when runtime filter is enabled and joined tables have the same column returned multiple times (e.g. SELECT a, a, a FROM t). #93526 (Alexander Gololobov).
• Fix a bug where clickhouse-client would ask for password twice when connecting using ssh. #93547 (Isak Ellmer).
• Make sure that zookeeper is finalized on shutdown (fix possible hung on shutdown in very unlikely cases). #93602 (Azat Khuzhin).
• Fix LOGICAL_ERROR when restoring ReplicatedMergeTree with deduplication race. #93612 (Pablo Marcos).
• Fix using Sparse column for TTL update during direct deserialization into Sparse columns in some input formats. It fixes possible logical error Unexpected type of result TTL column. #93619 (Pavel Kruglov).
• Fixed h3 index functions sometimes crashing or getting stuck when called on invalid inputs. #93657 (Michael Kolupaev).
• The usage of ngram_bf index on a non-UTF-8 data led to an uninitialized memory read, with values that could reside in the resulting index structure. Closes #92576. #93663 (Alexey Milovidov).
• Validate that the decompressed buffer size is as expected. #93690 (Raúl Marín).
• Prevent users to get the list of columns from a table without checking SHOW COLUMNS permission using the merge table engine. #93695 (János Benjamin Antal).
• Fixed materialization of skip indexes created on top of subcolumns. #93708 (Anton Popov).
• We store storages' shared pointers in QueryPipeline::resources::storage_holders to make sure that the IStorage objects are not destroyed while PipelineExecutor is alive. #93746 (Miсhael Stetsyuk).
• Fix attaching Replicated DBs when the interserver host changed after restarting. #93779 (Tuan Pham Anh).
• Fix assert !read_until_position in ReadBufferFromS3 which happened when cache is enabled. #93809 (Kseniia Sumarokova).
• Fix logical error in a rare case when empty tuple is used with Map column. Closes #93784. #93814 (Nihal Z. Miaji).
• Fixed _part_offset corruption when projections are rebuilt during merges, and optimized projection processing by avoiding unnecessary reads of the _part_offset column and skipping unneeded columns in projection calculations. This continues the optimizations introduced in #93233. #93827 (Amos Bird).
• Remove 'Bad version' handling. #93843 (Anton Ivashkin).
• Fix optimize_inverse_dictionary_lookup not working with distributed query when key is signed integral type. Closes #93259. #93848 (Nihal Z. Miaji).
• Fix lag/lead not working with distributed remote() query. Closes #90014. #93858 (Nihal Z. Miaji).
• Fix system instrument dispatch bug. #93937 (Pablo Marcos).
• In https://github.com/ClickHouse/ClickHouse/pull/89173, we added an extra field to the structure that TraceSender sends through an internal pipe. However, the buffer size was not updated (here), therefore we are writing more data to buffer than buffer_size which results in multiple flushes. And because TraceSender::send is called from different threads, different threads' flushes may interleave which breaks the invariant that the receiving end (TraceCollector) relies on. #93966 (Miсhael Stetsyuk).
• Fix type conversion to super type during the join operation of the storage Join with USING clause. Fixes #91672. Fixes #78572. #94000 (Dmitry Novik).
• Fix for FilterStep not properly added when join runtime filter is applied over Merge table. #94021 (Alexander Gololobov).
• A SELECT query containing a predicate on multiple columns with bloom filter skip indexes and both OR and NOT conditions are present could return inconsistent results. That is fixed now. #94026 (Shankar Iyer).
• Fix CLEAR column with dependent indices. #94057 (Raúl Marín).
• Fix use-of-uninitialized-value in ReadWriteBufferFromHTTP. #94058 (Alexey Milovidov).
• Fix bad check for typed paths in JSON. The check was introduced in https://github.com/ClickHouse/ClickHouse/pull/92842 and can lead to an error during existing tables startup. #94070 (Pavel Kruglov).
• Fix the crash during filter analysis in the presence of OUTER JOIN. Fixes #90979. #94080 (Dmitry Novik).
• Fix accuracy of uniqTheta when using UInt8 aggregation keys in parallel (max_threads > 1 - default). #94095 (Azat Khuzhin).
• Fix crash caused by exception thrown from a socket.setBlocking(true) call inside SCOPE_EXIT. #94100 (Miсhael Stetsyuk).
• Fix data loss when DROP PARTITION removes parts created by later log entries in ReplicatedMergeTree. #94123 (Tuan Pham Anh).
• Fixed parquet reader v3 incorrectly handling arrays that cross page boundaries. This happens e.g. for files written by Arrow without enabling page statistics or page index. Affects only columns of Array data type. Likely symptom is that one array every ~1 MB of data gets truncated. Before this fix, use this setting as workaround: input_format_parquet_use_native_reader_v3 = 0. #94125 (Michael Kolupaev).
• Fix too many watches in ReplicatedMergeTree while waiting for log entry. #94133 (Azat Khuzhin).
• Functions arrayShuffle, arrayPartialShuffle and arrayRandomSample to materialize const columns - so that different rows get different results. #94134 (Joanna Hulboj).
• Fix data race in evaluating table functions in materialized views. #94171 (Alexey Milovidov).
• Fix nullptr dereference in PostgreSQL database engines (when the query is incorrect). Closes #92887. #94180 (Alexey Milovidov).
• Fix memory leak in refreshable materialized views using SELECT queries with multiple subqueries. #94200 (Antonio Andelic).
• Fix data race in DataPartStorageOnDiskBase::remove vs system.parts. Closes #49076. #94262 (Alexey Milovidov).
• Remove the wrong noexcept specifier at HashTable copy assignment that may lead to crash (std::terminate) on memory exceptions. #94275 (Nikita Taranov).
• Previously, creating a projection with duplicate columns in GROUP BY (e.g., GROUP BY c0, c0) and inserting data caused a std::length_error if optimize_row_order is enabled. Closes #94065. #94277 (Alexey Milovidov).
• Fix obscure bug in ZooKeeper client on connect which leads to hungs and crashes. #94320 (Azat Khuzhin).
• Fix function to subcolumns optimization not applied to subcolumns. #94323 (Pavel Kruglov).
• Fix possibly incorrect result in nested RIGHT JOINs when enable_lazy_columns_replication is enabled. The bug caused all rows in replicated columns to incorrectly return the same value instead of their distinct values. Close #93891. #94339 (Vladimir Cherkasov).
• Fix filter pushdown for SEMI JOIN using equivalence sets. Do not push the filter down if argument types have changed. Fixes #93264. #94340 (Dmitry Novik).
• Fix usage of DeltaLake CDF with database DataLake database engine (delta lake catalogs integration). Closes #94122. #94342 (Kseniia Sumarokova).
• Fix incorrect value of current metric FilesystemCacheSizeLimit in case SLRU cache policy was used. #94363 (Kseniia Sumarokova).
• Creating a Backup database engine with less than two arguments now returns a more descriptive error message (Wrong number of arguments instead of std::out_of_range: InlinedVector::at(size_type) const failed bounds check.). #94374 (Robert Schulze).
• Ignores impossible revokes of global grants on the database level for grants with grant option. #94386 (pufit).
• Fix reading sparse offsets from compact parts. Closes #94385. #94399 (Pavel Kruglov).
• Don't prevent ALTER of columns using implicit indexes, even if alter_column_secondary_index_mode's throw mode is used. #94425 (Raúl Marín).
• Fix crash in TCPHandler when multiple receivePacketsExpectQuery calls read Protocol::Client::IgnoredPartUUIDs. #94434 (Miсhael Stetsyuk).
• Fix masking sensitive data in system.functions. #94436 (Vitaly Baranov).
• Fix nullptr dereference with disabled send_profile_events. This feature was introduced recently for the ClickHouse Python driver. Closes #92488. #94466 (Alexey Milovidov).
• Fix text index .mrk incompatibility during merges. #94494 (Peng Jian).
• When read_in_order_use_virtual_row is enabled, the code was accessing index columns based on the full primary key size without checking if the index was truncated, leading to use-after-free / uninitialized memory. Closes #85596. #94500 (Alexey Milovidov).
• Fix an error due to a type mismatch when sending external tables for subqueries with GLOBAL IN if the types are Nullable. Closes #94097. #94511 (Alexey Milovidov).
• In previous versions, queries with multiple index conditions over the same expression may erroneously throw an exception Not found column. Closes #60660. #94515 (Alexey Milovidov).
• Fix incorrect handling of Nullable join column in runtime filters. #94555 (Alexander Gololobov).
• Creating a workload in another workload that is currently in use no longer causes a crash. #94599 (Sergei Trifonov).
• Fix a crash during ANY LEFT JOIN optimization when isNotNull is evaluated on a missing column. #94600 (Molly).
• Fix default expression evaluation when referencing other columns with computed defaults. #94615 (Alexey Milovidov).
• Fix permission issues in BACKUP/RESTORE operations. #94617 (Pablo Marcos).
• Fix crash due to incorrect type cast when the data type is Nullable(DateTime64). #94627 (Miсhael Stetsyuk).
• Fixes a bug where certain distributed queries with ORDER BY could return ALIAS columns with swapped values (i.e., column a showing column b’s data and vice versa). #94644 (filimonov).
• Fix storing results of keeper-bench to file. #94654 (Antonio Andelic).
• Fix incorrect estimations with MinMax-type statistics when the column contains negative floating-point values. #94665 (zoomxi).
• Fix reading Parquet files when a map's key is a struct. #94670 (Konstantin Vedernikov).
• Fix possibly incorrect RIGHT join result when using complex ON conditions. Close #92913. #94680 (Vladimir Cherkasov).
• Preserve constant index granularity (use_const_adaptive_granularity) after Vertical merges. #94725 (Azat Khuzhin).
• Fix mutation bug with scalar subqueries and table dependencies. If a table had dependencies (index or projections) over a column, scalar subqueries might be evaluated and cached without data and lead to incorrect changes. #94731 (Raúl Marín).
• Fix AsynchronousMetrics cpu_pressure fallback on error. #94827 (Raúl Marín).
• The getURLHostRFC function was missing bounds checks before dereferencing pointers. When an empty string was passed to domainRFC, it would read uninitialized memory, triggering MSan errors. #94851 (Alexey Milovidov).
• Fix readonlyness of encrypted disks. #94852 (Azat Khuzhin).
• Fix logical error in fractional LIMIT/OFFSET when using the old analyzer with Distributed tables. Closes #94712. #94999 (Ahmed Gouda).
• Fix crash under some conditions when join runtime filters are enabled by default. #95000 (Alexander Gololobov).
• Improve masking passwords in url used in table engine URL() and table function url(). #95006 (Vitaly Baranov).
• Function toStartOfInterval now works in the same way as toStartOfX, where X is Day, Week, Month, Quarter, Year when the enable_extended_results_for_datetime_functions is on. #95011 (Kirill Kopnev).
• Fix constant string comparisons not respecting the settings cast_string_to_date_time_mode, bool_true_representation, bool_false_representation, and input_format_null_as_default. Closes #91681. #95040 (Nihal Z. Miaji).
• Fix data race in the filesystem cache. #95064 (Alexey Milovidov).
• Fix a rare race condition in the Parquet reader. #95068 (Alexey Milovidov).
• Fix crash in the top K optimization when LIMIT is zero. Closes #93893. #95072 (Alexey Milovidov).
• Converting from DateTime/integers to Time64 extracts the time-of-day component using toTime, which is not monotonic. The ToDateTimeMonotonicity template incorrectly claimed this conversion was monotonic, causing "Invalid binary search result in MergeTreeSetIndex" exception in debug builds. #95125 (Alexey Milovidov).
• Recreated list of manifest file entries only if necessary (previously it was done on each iteration). #95162 (Daniil Ivanik).

Build/Testing/Packaging Improvement

• Add a set of tools for profiling memory allocations in the ClickHouse SQL parser using jemalloc's heap profiling capabilities. #94072 (Ilya Yatsishin).
• Added a tool that simplifies debugging of memory allocations in parser. It uses jemalloc stats.allocated metric before and after we parse query to AST representation to show what is allocated. Also it supports memory profiling mode that dumps profile before and after to build reports where allocations occurred. #93523 (Ilya Yatsishin).
• Remove transitive libc++ includes. #92523 (Raúl Marín).
• Make some sequential tests parallel: https://github.com/ClickHouse/ClickHouse/pull/93030/changes#diff-c3a73510dae653c9bbfa24300b32f5d6ec663fd4e72cc4a3d5daa6e4342915df. #93030 (Nikita Fomichev).
• Cleanup some build flags. #93679 (Raúl Marín).
• Bump c-ares from v1.34.5 to v1.34.6. This addresses c-ares' CVE-2025-62408, which is not relevant for ClickHouse. #94129 (Govind R Nair).
• Use curl 8.18.0. #94742 (Konstantin Bogdanov).