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TiDB 5.2.2 Release Notes
TiDB 5.2.2 was released on October 29, 2021. The release includes various improvements and bug fixes for TiDB, TiKV, PD, TiCDC, TiFlash, and TiDB Binlog. Improvements include showing affected SQL statements in debug logs, support for showing backup and restore data size, and more. Bug fixes address issues such as plan-cache detection, wrong partition pruning, and various other issues related to query functions, client connections, and data replication.

TiDB 5.2.2 Release Notes

Release Date: October 29, 2021

TiDB version: 5.2.2

Improvements

  • TiDB

    • Show the affected SQL statements in the debug log when the coprocessor encounters a lock, which is helpful in diagnosing problems #27718
    • Support showing the size of the backup and restore data when backing up and restoring data in the SQL logical layer #27247

  • TiKV

    • Simplify the algorithm of L0 flow control #10879
    • Improve the error log report in the raft client module #10983
    • Improve logging threads to avoid them becoming a performance bottleneck #10841
    • Add more statistics types of write queries #10507

  • PD

    • Add more types of write queries to QPS dimensions in the hotspot scheduler #3869
    • Support dynamically adjusting the retry limit of the balance region scheduler to improve the performance of the scheduler #3744
    • Update TiDB Dashboard to v2021.10.08.1 #4070
    • Support that the evict leader scheduler can schedule regions with unhealthy peers #4093
    • Speed up the exit process of schedulers #4146

  • Tools

    • TiCDC

      • Reduce the default value of the Kafka sink configuration item MaxMessageBytes from 64 MB to 1 MB to fix the issue that large messages are rejected by the Kafka Broker #3104
      • Reduce memory usage in the relpication pipeline #2553 #3037 #2726
      • Optimize monitoring items and alert rules to improve observability of synchronous links, memory GC, and stock data scanning processes #2735 #1606 #3000 #2985 #2156
      • When the sync task status is normal, no more historical error messages are displayed to avoid misleading users #2242

Bug Fixes

  • TiDB

    • Fix the issue that plan-cache cannot detect changes of unsigned flags #28254
    • Fix the wrong partition pruning when the partition function is out of range #28233
    • Fix the issue that planner might cache invalid plans for join in some cases #28087
    • Fix wrong index hash join when hash column type is enum #27893
    • Fix a batch client bug that recycling idle connection might block sending requests in some rare cases #27688
    • Fix the TiDB Lightning panic issue when it fails to perform checksum on a target cluster #27686
    • Fix wrong results of the date_add and date_sub functions in some cases #27232
    • Fix wrong results of the hour function in vectorized expression #28643
    • Fix the authenticating issue when connecting to MySQL 5.1 or an older client version #27855
    • Fix the issue that auto analyze might be triggered out of the specified time when a new index is added #28698
    • Fix a bug that setting any session variable invalidates tidb_snapshot #28683
    • Fix a bug that BR is not working for clusters with many missing-peer regions #27534
    • Fix the unexpected error like tidb_cast to Int32 is not supported when the unsupported cast is pushed down to TiFlash #23907
    • Fix the issue that DECIMAL overflow is missing in the %s value is out of range in '%s'error message #27964
    • Fix a bug that the availability detection of MPP node does not work in some corner cases #3118
    • Fix the DATA RACE issue when assigning MPP task ID #27952
    • Fix the INDEX OUT OF RANGE error for a MPP query after deleting an empty dual table. #28250
    • Fix the issue of false positive error log invalid cop task execution summaries length for MPP queries #1791
    • Fix the issue of error log cannot found column in Schema column for MPP queries #28149
    • Fix the issue that TiDB might panic when TiFlash is shutting down #28096
    • Remove the support for insecure 3DES (Triple Data Encryption Algorithm) based TLS cipher suites #27859
    • Fix the issue that Lightning connects to offline TiKV nodes during pre-check and causes import failures #27826
    • Fix the issue that pre-check cost too much time when importing many files to tables #27605
    • Fix the issue that rewriting expressions makes between infer wrong collation #27146
    • Fix the issue that group_concat function did not consider the collation #27429
    • Fix the result wrong that occurs when the argument of the extract function is a negative duration #27236
    • Fix the issue that creating partition fails if NO_UNSIGNED_SUBTRACTION is set #26765
    • Avoid expressions with side effects in column pruning and aggregation pushdown #27106
    • Remove useless gRPC logs #24190
    • Limit the valid decimal length to fix precision-related issues #3091
    • Fix the issue of a wrong way to check for overflow in plus expression #26977
    • Fix the issue of data too long error when dumping statistics from the table with new collation data #27024
    • Fix the issue that the retried transactions' statements are not included in TIDB_TRX #28670

  • TiKV

    • Fix the issue that CDC adds scan retries frequently due to the Congest error #11082
    • Fix the issue that the raft connection is broken when the channel is full #11047
    • Fix the issue that batch messages are too large in Raft client implementation #9714
    • Fix the issue that some coroutines leak in resolved_ts #10965
    • Fix a panic issue that occurs to the coprocessor when the size of response exceeds 4 GiB #9012
    • Fix the issue that snapshot Garbage Collection (GC) misses GC snapshot files when snapshot files cannot be garbage collected #10813
    • Fix a panic issue caused by timeout when processing Coprocessor requests #10852

  • PD

    • Fix the issue that PD incorrectly delete the peers with data and in pending status because the number of peers exceeds the number of configured peers #4045
    • Fix the issue that PD does not fix down peers in time #4077
    • Fix the issue that the scatter range scheduler cannot schedule empty regions #4118
    • Fix the issue that the key manager cost too much CPU #4071
    • Fix the data race issue that might occur when setting configurations of hot region scheduler #4159
    • Fix slow leader election caused by stuck region syncer #3936

  • TiFlash

    • Fix the issue that TiFlash fails to start up on some platforms due to the absence of library nsl

  • Tools

    • TiCDC

      • Fix the issue that TiCDC replication task might terminate when the upstream TiDB instance unexpectedly exits #3061
      • Fix the issue that TiCDC process might panic when TiKV sends duplicate requests to the same Region #2386
      • Fix unnecessary CPU consumption when verifying downstream TiDB/MySQL availability #3073
      • Fix the issue that the volume of Kafka messages generated by TiCDC is not constrained by max-message-size #2962
      • Fix the issue that TiCDC sync task might pause when an error occurs during writing a Kafka message #2978
      • Fix the issue that some partitioned tables without valid indexes might be ignored when force-replicate is enabled #2834
      • Fix the issue that scanning stock data might fail due to TiKV performing GC when scanning stock data takes too long #2470
      • Fix a possible panic issue when encoding some types of columns into Open Protocol format #2758
      • Fix a possible panic issue when encoding some types of columns into Avro format #2648

    • TiDB Binlog

      • Fix the issue that when most tables are filtered out, checkpoint cannot be updated under some special load #1075