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TiDB 5.0.2 Release Notes
TiDB 5.0.2 was released on June 10, 2021. The new version includes compatibility changes, new features, improvements, bug fixes, and updates to various tools such as TiKV, TiFlash, PD, TiCDC, Backup & Restore (BR), and TiDB Lightning. Some notable changes include the deprecation of `--sort-dir` in TiCDC, enabling the Hibernate Region feature in TiKV, and various bug fixes in TiDB, TiKV, PD, TiFlash, and tools like TiCDC, BR, and TiDB Lightning.

TiDB 5.0.2 Release Notes

Release date: June 10, 2021

TiDB version: 5.0.2

Compatibility Changes

  • Tools

    • TiCDC

      • Deprecate --sort-dir in the cdc cli changefeed command. Instead, users can set --sort-dir in the cdc server command. #1795

New Features

  • TiKV

    • Enable the Hibernate Region feature by default #10266

Improvements

  • TiDB

    • Avoid frequently reading the mysql.stats_histograms table if the cached statistics is up-to-date to avoid high CPU usage #24317

  • TiKV

    • BR now supports the S3-compatible storage using the virtual-host addressing mode #10243
    • Support the back pressure for TiCDC's scan speed #10151
    • Reduce the memory usage of TiCDC's initial scan #10133
    • Improve the cache hit ratio of the TiCDC's Old Value feature in the pessimistic transaction #10089
    • Split Regions more evenly to mitigate the issue that the growth of Region size exceeds the splitting speed when there are hotspot writes #9785

  • TiFlash

    • Optimize the table lock to prevent DDL jobs and data reads from blocking each other
    • Support casting the INTEGER or REAL type to REAL type

  • Tools

    • TiCDC

      • Add monitoring metrics for the table memory consumption #1885
      • Optimize the memory and CPU usages during the sorting stage #1863
      • Delete some useless log information that might cause user confusion #1759

    • Backup & Restore (BR)

      • Clarify some ambiguous error messages #1132
      • Support checking the cluster version of a backup #1091
      • Support backing up and restoring system tables in the mysql schema #1143 #1078

    • Dumpling

      • Fix the issue that no error is output when a backup operation fails #280

Bug Fixes

  • TiDB

    • Fix the panic issue caused by using the prefix index and index join in some cases #24547 #24716 #24717
    • Fix the issue that the prepared plan cache of point get is incorrectly used by the point get statement in the transaction #24741
    • Fix the issue of writing the wrong prefix index value when the collation is ascii_bin or latin1_bin #24569
    • Fix the issue that the ongoing transaction might be interrupted by the GC worker #24591
    • Fix a bug that the point query might get wrong on the clustered index when new-collation is enabled but new-row-format is disabled #24541
    • Refactor the conversion of partition keys for shuffle hash join #24490
    • Fix the panic issue that occurs when building the plan for queries that contain the HAVING clause #24045
    • Fix the issue that the column pruning improvement causes the Apply and Join operators' results to go wrong #23887
    • Fix a bug that the primary lock fallen back from async commit cannot be resolved #24384
    • Fix a GC issue of statistics that might cause duplicated fm-sketch records #24357
    • Avoid unnecessary pessimistic rollback when the pessimistic locking receives the ErrKeyExists error #23799
    • Fix the issue that numeric literals cannot be recognized when the sql_mode contains ANSI_QUOTES #24429
    • Forbid statements such as INSERT INTO table PARTITION (<partitions>) ... ON DUPLICATE KEY UPDATE to read data from non-listed partitions #24746
    • Fix the potential index out of range error when a SQL statement contains both GROUP BY and UNION #24281
    • Fix the issue that the CONCAT function incorrectly handles the collation #24296
    • Fix the issue that the collation_server global variable does not take effect in new sessions #24156

  • TiKV

    • Fix a TiCDC OOM issue caused by reading old values #9996 #9981
    • Fix the issue of empty value in the secondary index for the clustered primary key column when collation is latin1_bin #24548
    • Add the abort-on-panic configuration, which allows TiKV to generate the core dump file when panic occurs. Users still need to correctly configure the environment to enable core dump #10216
    • Fix the performance regression issue of point get queries that occurs when TiKV is not busy #10046

  • PD

    • Fix the issue that the PD Leader re-election is slow when there are many stores #3697
    • Fix the panic issue that occurs when removing the evict leader scheduler from a non-existent store #3660
    • Fix the issue that the statistics are not updated after offline peers are merged #3611

  • TiFlash

    • Fix the issue of incorrect results when cloning shared delta index concurrently
    • Fix the potential issue that TiFlash fails to restart with incomplete data
    • Fix the issue that old dm files are not removed automatically
    • Fix the potential panic that occurs when the Compaction Filter feature is enabled
    • Fix the potential issue that ExchangeSender sends duplicated data
    • Fix the issue that TiFlash cannot resolve the lock fallen back from async commit
    • Fix the issue of incorrect results returned when the casted result of the TIMEZONE type contains the TIMESTAMP type
    • Fix the TiFlash panic issue that occurs during Segment Split
    • Fix the issue that the execution information about the non-root MPP task is not accurate

  • Tools

    • TiCDC

      • Fix the issue that the time zone information is lost in the Avro output #1712
      • Support cleaning up stale temporary files in Unified Sorter and forbid sharing the sort-dir directory #1742
      • Fix a deadlock bug in the KV client that occurs when many stale Regions exist #1599
      • Fix the wrong help information in the --cert-allowed-cn flag #1697
      • Revert the update for explicit_defaults_for_timestamp which requires the SUPER privilege when replicating data to MySQL #1750
      • Support the sink flow control to reduce the risk of memory overflow #1840
      • Fix a bug that the replication task might stop when moving a table #1828
      • Fix the issue that the TiKV GC safe point is blocked due to the stagnation of TiCDC changefeed checkpoint #1759

    • Backup & Restore (BR)

      • Fix the issue that the DELETE events are lost during the log restore #1063
      • Fix a bug that causes BR to send too many useless RPC requests to TiKV #1037
      • Fix the issue that no error is output when a backup operation fails #1043

    • TiDB Lightning

      • Fix the issue of TiDB Lightning panic that occurs when generating KV data #1127
      • Fix the issue that TiDB Lightning in the TiDB-backend mode cannot load any data when the autocommit is disabled #1104
      • Fix a bug that the batch split Region fails due to the total key size exceeding the raft entry limit during the data import #969