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 shuting 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 can not be updated under some special load #1075