tasks/common/persistence/cassandra/schema_version_reader.go

// The MIT License
//
// Copyright (c) 2020 Temporal Technologies Inc.  All rights reserved.
//
// Copyright (c) 2020 Uber Technologies, Inc.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.

package cassandra

import (
	"errors"

	"go.temporal.io/server/common/persistence/nosql/nosqlplugin/cassandra/gocql"
)

const (
	readSchemaVersionCQL = `SELECT curr_version from schema_version where keyspace_name=?`
)

type (
	SchemaVersionReader struct {
		session gocql.Session
	}
)

var (
	ErrGetSchemaVersion = errors.New("failed to get current schema version from cassandra")
)

func NewSchemaVersionReader(session gocql.Session) *SchemaVersionReader {
	return &SchemaVersionReader{
		session: session,
	}
}

// ReadSchemaVersion returns the current schema version for the Keyspace
func (svr *SchemaVersionReader) ReadSchemaVersion(keyspace string) (string, error) {
	query := svr.session.Query(readSchemaVersionCQL, keyspace)

	iter := query.Iter()
	var version string
	if !iter.Scan(&version) {
		_ = iter.Close()
		return "", ErrGetSchemaVersion
	}
	if err := iter.Close(); err != nil {
		return "", err
	}
	return version, nil
}