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release-4.0.14.md

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TiDB 4.0.14 Release Notes
TiDB 4.0.14 was released on July 27, 2021. The release includes compatibility changes, feature enhancements, improvements, bug fixes, and updates to various tools. Some notable changes include default value updates for TiDB and TiKV, support for OIDC SSO in TiDB Dashboard, and bug fixes for TiDB, TiKV, PD, TiFlash, and various tools.

TiDB 4.0.14 Release Notes

Release date: July 27, 2021

TiDB version: 4.0.14

Compatibility changes

  • TiDB

    • Change the default value of tidb_multi_statement_mode from WARN to OFF in v4.0. It is recommended to use the multi-statement feature of your client library instead. See the documentation on tidb_multi_statement_mode for details. #25749
    • Upgrade Grafana dashboard from v6.1.16 to v7.5.7 to solve two security vulnerabilities. See the Grafana blog post for details.
    • Change the default value of the tidb_stmt_summary_max_stmt_count variable from 200 to 3000 #25872

  • TiKV

    • Change the default value of merge-check-tick-interval from 10 to 2 to speed up the Region merge process #9676

Feature enhancements

  • TiKV

    • Add a metric pending to monitor the number of pending PD heartbeats, which helps locate the issue of slow PD threads #10008
    • Support using the virtual-host addressing mode to make BR support the S3-compatible storage #10242

  • TiDB Dashboard

    • Support OIDC SSO. By setting the OIDC-compatible SSO services (such as Okta and Auth0), users can log into TiDB Dashboard without entering the SQL password. #960
    • Add the Debug API UI, which is an alternative method to the command line to call several common TiDB and PD internal APIs for advanced debugging #927

Improvements

  • TiDB

    • Change the LOCK record into the PUT record for the index keys using point get or batch point get for UPDATE reads #26223
    • Support the MySQL system variable init_connect and its associated features #26031
    • Support the stable result mode to make the query results more stable #26003
    • Support pushing down the built-in function json_unquote() to TiKV #25721
    • Make the SQL Plan Management (SPM) not affected by the character set #23295

  • TiKV

    • Shutdown the status server first to make sure that the client can correctly check the shutdown status #10504
    • Always respond to stale peers to make sure that these peers are cleared quicker #10400
    • Limit the TiCDC sink's memory consumption #10147
    • When a Region is too large, use the even split to speed up the split process #10275

  • PD

    • Reduce the conflicts among multiple schedulers that run at the same time #3858 #3854

  • TiDB Dashboard

    • Update TiDB Dashboard to v2021.07.17.1 #3882
    • Support sharing the current session as a read-only session to avoid further modification to it #960

  • Tools

    • Backup & Restore (BR)

      • Speed up restore by merging small backup files #655

    • Dumpling

      • Always split tables using _tidb_rowid when the upstream is a TiDB v3.x cluster, which helps reduce TiDB's memory usage #306

    • TiCDC

      • Improve the error message returned when a PD endpoint misses the certificate #1973
      • Make the sorter I/O errors more user-friendly #1976
      • Add a concurrency limit on the Region incremental scan in the KV client to reduce the pressure of TiKV #1926
      • Add metrics for the table memory consumption #1884
      • Add capture-session-ttl to the TiCDC server configuration #2169

Bug fixes

  • TiDB

    • Fix the issue that the SELECT result is incompatible with MySQL when joining a subquery with a WHERE clause evaluated to false #24865
    • Fix the calculation error of the ifnull function that occurs when the argument is the ENUM or SET type #24944
    • Fix the wrong aggregate pruning in some cases #25202
    • Fix the incorrect result of the merge join operation that might occur when the column is the SET type #25669
    • Fix the issue that TiDB returns wrong results for cartesian join #25591
    • Fix the panic issue that occurs when SELECT ... FOR UPDATE works on a join operation and the join uses a partitioned table #20028
    • Fix the issue that the cached prepared plan is incorrectly used for point get #24741
    • Fix the issue that the LOAD DATA statement can abnormally import non-utf8 data #25979
    • Fix a potential memory leak issue that occurs when accessing the statistics via an HTTP API #24650
    • Fix a security issue that occurs when executing the ALTER USER statement #25225
    • Fix a bug that the TIKV_REGION_PEERS table cannot correctly handle the DOWN status #24879
    • Fix the issue that invalid strings are not truncated when parsing DateTime #22231
    • Fix the issue that the select into outfile statement might have no result when the column type is YEAR #22159
    • Fix the issue that the query result might be wrong when NULL is in the UNION subquery #26532
    • Fix the issue that the projection operator in execution might cause panic in some cases #26534

  • TiKV

    • Fix the issue that the duration calculation might panic on certain platforms #related-issue
    • Fix the wrong function that casts DOUBLE to DOUBLE #25200
    • Fix the issue that the panic log might be lost when using the async logger #8998
    • Fix the panic issue that occurs when building a snapshot twice if encryption is enabled #9786 #10407
    • Fix the wrong arguments type of the json_unquote() function in the coprocessor #10176
    • Fix the issues of suspicious warnings during shutdown and the non-deterministic response from Raftstore #10353 #10307
    • Fix the issue of backup threads leak #10287
    • Fix the issue that Region split might panic and corrupt the metadata if the split process is too slow and Region merge is on-going #8456 #8783
    • Fix the issue that the Region heartbeats prevent TiKV from splitting large Regions in some situations #10111
    • Fix the wrong statistics caused by the format inconsistency of CM Sketch between TiKV and TiDB #25638
    • Fix the wrong statistics of the apply wait duration metric #9893
    • Fix the "Missing Blob" error after using delete_files_in_range in Titan #10232

  • PD

    • Fix a bug that the scheduler might reappear after executing the delete operation #2572
    • Fix the data race issue that might occur when the scheduler is started before the temporary configuration is loaded #3771
    • Fix a PD panic issue that might occur during the Region scattering operation #3761
    • Fix the issue that the priority of some operators is not set correctly #3703
    • Fix a PD panic issue that might occur when deleting the evict-leader scheduler from a non-existent store #3660
    • Fix the issue that the PD Leader re-election is slow when there are many stores #3697

  • TiDB Dashboard

    • Fix the issue that the Profiling UI cannot profile all TiDB instances #944
    • Fix the issue that the Statements UI does not display "Plan Count" #939
    • Fix the issue that the Slow Query UI might display the "unknown field" error after cluster upgrade #902

  • TiFlash

    • Fix the potential panic issue that occurs when compiling DAG requests
    • Fix the panic issue that occurs when the read load is heavy
    • Fix the issue that TiFlash keeps restarting because of the split failure in column storage
    • Fix a potential bug that TiFlash cannot delete the delta data
    • Fix the incorrect results that occur when cloning the shared delta index concurrently
    • Fix a bug that TiFlash fails to restart in the case of incomplete data
    • Fix the issue that the old dm files cannot be removed automatically
    • Fix the panic issue that occurs when executing the SUBSTRING function with specific arguments
    • Fix the issue of incorrect results when casting the INTEGER type to the TIME type

  • Tools

    • Backup & Restore (BR)

      • Fix the issue that the data restore from the mysql schema might fail #1142

    • TiDB Lightning

      • Fix the issue that TiDB Lightning fails to parse the DECIMAL type data in Parquet files #1276
      • Fix the EOF error reported when TiDB Lightning splits the imported large CSV files #1133
      • Fix a bug that an excessively large base value is generated when TiDB Lightning imports tables with the auto_increment column of the FLOAT or DOUBLE type #1185
      • Fix the issue of TiDB Lightning panic that occurs when generating KV data larger than 4 GB #1128

    • Dumpling

      • When using Dumpling to export data to the S3 storage, the s3:ListBucket permission is no longer required on the entire bucket. The permission is required only on the data source prefix. #898

    • TiCDC

      • Fix the issue of extra partition dispatching after adding new table partitions #2205
      • Fix the panic issue that occurs when TiCDC fails to read /proc/meminfo #2023
      • Reduce TiCDC's runtime memory consumption #2011 #1957
      • Fix a bug that some MySQL connection might leak after MySQL sink meets the error and pauses #1945
      • Fix the issue that TiCDC changefeed cannot be created when start TS is less than current TS minus GC TTL #1839
      • Reduce memory malloc in sort heap to avoid too much CPU overhead #1853
      • Fix a bug that the replication task might stop when moving a table #1827