This topic describes the release notes for the PolarDB-X storage engine.

The version of the storage engine of a PolarDB-X instance is updated to the most recent version when you update the version of the PolarDB-X instance to the most recent version. A version number of a PolarDB-X instance consists of the version of the PolarDB-X kernel and the version of the storage engine, such as kernel_5.4.12-16349923_xcluster-20210926. xcluster-20210926 indicates the version of the storage engine.

Release date: 2022-04-29

Version: xcluster-20220429

Type Description
Fixed issues The following issue is fixed: Read operations and write operations cannot be performed when the thd->get_protocol command is run.
The following issue is fixed: Errors occur during the execution of prepared statements that include sequences of the New Sequence type.
The following issue is fixed: Large files cannot be purged in a quick manner.
The following issue is fixed: Specific characters that are included in JSON-format data cannot be correctly escaped.
The following issue is fixed: Memory leaks occur when the system collects statistics at the schema level.

Release date: 2022-04-21

Version: xcluster-20220421

Type Description
New feature A new sequence engine is supported.

Release date: 2022-03-31

Version: xcluster-20220331

Type Description
New feature The port check feature is provided. When a data node starts, the system checks whether the port that is used to send requests over the PolarDB-X proprietary protocol is being used by another process. If the port is being used by another process, the current process automatically exits.
Fixed issue The following issue is fixed: When data chunks are transmitted over the PolarDB-X proprietary protocol, the corresponding data nodes crash due to data leaks.

Release date: 2022-02-24

Version: xcluster-20220224

Type Description
Fixed issues The following issue is fixed: When a Bloom filter is used, data boundary errors occur if the result that is obtained by dividing the length of an element that is calculated by using the xxHash algorithm by 8 is equal to 4.
The following issue is fixed: Compatibility errors occur after the value of innodb_thread_concurrency is changed.

Release date: 2021-12-15

Version: xcluster-20211215

Type Description
Fixed issues Redundant rotate events are removed from binary logs.
The following issue is fixed: The previous version of MySQL plugins may be used after the storage engine is updated and the deployment script is run to deploy data nodes.

Release date: 2021-11-16

Version: xcluster-20211116

Type Description
New features The xxHash algorithm is supported for Bloom filters.
Raw strings are supported, and the issue in which precision loss occurs for decimal values is fixed in PolarDB-X kernel V5.4.13 and later versions.
The purge sequence feature is provided. The system can automatically increase the value of the lower threshold for data purging to support long-term transactions.
Fixed issues The following issue is fixed: Faster Checker returns incorrect hash values if Faster Checker does not obtain data.
The following issue is fixed: Data nodes crash when a graceful shutdown is performed for a Least Recently Used (LRU) cache.
The following issue is fixed: Followers can obtain locks.
The following issue is fixed: The corresponding data nodes crash when a graceful shutdown is performed for the Global Timestamp Service (GTS).
The following issue is fixed: Results of de-perimeterization for parameters of the bytes type are incorrect.

Release date: 2021-09-26

Version: xcluster-20210926

Type Description
New features The instant add column feature is provided.
The user defined function (UDF) fast hash checker component is provided.
Fixed issues The following issue is fixed: Token errors occur when requests are sent over the PolarDB-X proprietary protocol.
The following issue is fixed: The network layer may reject requests that are sent over the PolarDB-X proprietary protocol.

Release date: 2021-08-05

Version: xcluster-20210805

Type Description
New features The returning syntax is supported.
A lock-free algorithm is provided for Timestamp Oracle (TSO) to generate timestamps.

Release date: 2021-07-28

Version: xcluster-20210728

Type Description
Fixed issue The following issue is fixed: The corresponding data nodes crash when the system performs data sampling.

Release date: 2021-07-19

Version: xcluster-20210719

Type Description
Optimized feature Log content is optimized.
Fixed issues The following issue is fixed: The Visual Inertial Odometry (VIO) for sessions that are established over the PolarDB-X proprietary protocol crash.
The following issue is fixed: Table leaks occur when the lease of the GTS does not exist.

Release date: 2021-07-07

Version: xcluster-20210707

Type Description
Fixed issue The following issue is fixed: Sessions that are established over the PolarDB-X proprietary protocol cannot be terminated.

Release date: 2021-07-01

Version: xcluster-20210701

Type Description
Optimized feature The process of accessing transactions that are executed on a single shard is optimized.
Fixed issue The following issue is fixed: TSO returns incorrect results in batch processing mode. The algorithm that is used to distribute timestamps is modified.

Release date: 2021-06-28

Version: xcluster-20210628

Type Description
Fixed issue The following issue is fixed: When the PolarDB-X proprietary protocol is used to transmit execution plans to data nodes, the data nodes crash if operations that are not supported by the data nodes are included in execution plans. After this issue is fixed, data nodes report errors and do not crash in this scenario.

Release date: 2021-06-24

Version: xcluster-20210624

Type Description
New features The auto savepoint feature is provided.
The random sampling feature provided by InnoDB is supported.
By default, the polarx_udf plugin is enabled.
The feedback feature is provided to return the statistics of indexes and the number of rows.
Fixed issues The following issue is fixed: Transaction sequence leaks occur when transactions are processed over the PolarDB-X proprietary protocol.
The following issue is fixed: When the PolarDB-X proprietary protocol is used, the length of decimal values exceeds the upper limit if specific values are specified in double precision scenarios.
The following issue is fixed: Statistics of specific physical data are missing.
The following issue is fixed: The HLL service may crash.
The following issues are fixed: The batch timestamp generation feature of TSO does not take effect, and TSO may generate duplicate timestamps.
The following issue is fixed: The corresponding data nodes crash when utf8mb4 is used as a comparative parameter value in a filter expression that is executed over the PolarDB-X proprietary protocol.

Release date: 2021-03-30

Version: xcluster-20210330

Type Description
New features The cache feature is provided to cache SQL statements and execution plans of SQL queries that are executed over the PolarDB-X proprietary protocol.
The chunk transmission feature is provided to transmit data chunks over the PolarDB-X proprietary protocol.
Fixed issue The following issue is fixed: The system crashes when TSO transactions and DDL operations are performed in parallel.

Release date: 2021-03-11

Version: xcluster-20210311

Type Description
New feature The SQL flashback feature is provided.
Fixed issues The following issue is fixed: Unexpected prepare wait timeout issues occur when specific operations are performed.
The following issue is fixed: Data nodes crash in high concurrency scenarios.

Release date: 2021-02-04

Version: xcluster-20210204

Type Description
New feature The dump feature of mysqldump is supported. The system can back up data based on specified snapshot sequences.
Fixed issues The following issue is fixed: When enable_gts is enabled, binlog events are replayed from the earliest offset after a follower node is restarted.
The following issue is fixed: The leader node of an instance cannot be restored after the leader node is restarted.
By default, the lease period of the GTS is set to 2 seconds.
Commit timestamps (CTSs) can be included in messages that are transmitted over the PolarDB-X proprietary protocol, and the cache feature is provided to cache SQL statements and execution plans of SQL queries.

Release date: 2020-12-12

Version: xcluster-20201212

Type Description
New features TSO timestamps can be transmitted by using messages.
Common transactions can be committed in one-phase commit mode.
Fixed issues The following issue is fixed: Data nodes crash when the data types of parameters that are returned by UDFs of Bloom filters are incorrect.
The following issue is fixed: Null values and decimal values are not correctly processed by UDFs of Bloom filters.
The following issue is fixed: When CTS transactions are performed based on indexes, the isolation levels of the transactions are changed.
The issue in which an error occurs when one-phase commit transactions are performed is fixed.
Errors that are related to the XA protocol are resolved.

Release date: 2020-09-23

Version: xcluster-20200923

Type Description
New features The CTS persistence feature is provided.
Bloom filters that are created by using UDFs are supported.
UDFs are supported in HLL.
By default, the UDF module polarx_udf.so is loaded.
Optimized feature The authentication process for requests that are sent over the PolarDB-X proprietary protocol is optimized.
Fixed issues The following issue is fixed: Assert operations cause data nodes to crash.
Specific content is removed from logs that are recorded when the PolarDB-X proprietary protocol is used.

Release date: 2020-09-10

Version: xcluster-20200910

Type Description
New features A proprietary protocol is provided by PolarDB-X.
The TSO service is supported.
Timestamp-based distributed transactions are supported.
The primary-secondary consistent read feature is provided.
Fixed issues The following issue is fixed: After a server crashes during binlog rotation in an XA transaction, the XA transaction cannot be restored after the server is restarted.
The following issue is fixed: XA transactions cannot be replayed on follower nodes due to internal locks.
The following issue is fixed: When an XA_PREPARE_EVENT log event is performed, logs are incorrectly replayed and the data that is stored in the disk is incorrect.