TiDB 5.1.1 Release Notes

Release Date: July 30, 2021

TiDB version: 5.1.1

Compatibility changes

• TiDB

  • For TiDB clusters upgrade from v4.0 to v5.1, the default value of tidb_multi_statement_mode is OFF. It is recommended to use the multi-statement feature of your client library instead. See the documentation on tidb_multi_statement_mode for details. #25751
  • Change the default value of the tidb_stmt_summary_max_stmt_count variable from 200 to 3000 #25874
  • Require the SUPER privilege to access the table_storage_stats table #26352
  • Require the SELECT privilege on mysql.user to access the information_schema.user_privileges table to show other user's privileges #26311
  • Require the CONFIG privilege to access the information_schema.cluster_hardware table #26297
  • Require the PROCESS privilege to access the information_schema.cluster_info table #26297
  • Require the PROCESS privilege to access the information_schema.cluster_load table #26297
  • Require the PROCESS privilege to access the information_schema.cluster_systeminfo table #26297
  • Require the PROCESS privilege to access the information_schema.cluster_log table #26297
  • Require the CONFIG privilege to access the information_schema.cluster_config table #26150

Feature enhancements

• 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. #3883

• TiFlash

  • Support the HAVING() function in DAG requests

Improvements

• TiDB

  • Announce the general availability (GA) of the Stale Read feature
  • Avoid allocation for paramMarker to speed up data insertion #26076
  • Support the stable result mode to make the query results more stable #25995
  • Support pushing down the built-in function json_unquote() to TiKV #26265
  • Support retrying MPP queries #26480
  • Change the LOCK record into the PUT record for the index keys using point get or batch point get for UPDATE reads #26225
  • Forbid creating views from stale queries #26200
  • Thoroughly push down the COUNT(DISTINCT) aggregation function in the MPP mode #26194
  • Check the availability of TiFlash before launching MPP queries #26192
  • Do not allow setting the read timestamp to a future time #25763
  • Print log warnings when aggregation functions cannot be pushed down in EXPLAIN statements #25737
  • Add the statements_summary_evicted table to record the evicted count information of a cluster #25587
  • Improve the MySQL compatibility of the built-in function str_to_date for the format specifiers %b/%M/%r/%T #25768

• TiKV

  • Make the prewrite requests as idempotent as possible to reduce the chance of undetermined errors #10586
  • Prevent the risk of stack overflow when handling many expired commands #10502
  • Avoid excessive commit request retrying by not using the Stale Read request's start_ts to update max_ts #10451
  • Handle read ready and write ready separately to reduce read latency #10592
  • Reduce the impact on data import speed when the I/O rate limiting is enabled #10390
  • Improve the load balance between Raft gRPC connections #10495

• Tools

  • TiCDC

    • Remove file sorter #2327
    • Improve the error message returned when a PD endpoint misses the certificate #1973

  • TiDB Lightning

    • Add a retry mechanism for restoring schemas #1294

  • Dumpling

    • Always split tables using _tidb_rowid when the upstream is a TiDB v3.x cluster, which helps reduce TiDB's memory usage #295
    • Reduce the frequency of accessing the database metadata to improve Dumpling's performance and stability #315

Bug fixes

• TiDB

  • Fix the data loss issue that might occur when changing the column type with tidb_enable_amend_pessimistic_txn=on #26203
  • Fix the issue that the behavior of the last_day function is incompatible in the SQL mode #26001
  • Fix the panic issue that might occur when LIMIT is on top of window functions #25344
  • Fix the issue that committing pessimistic transactions might cause write conflict #25964
  • Fix the issue that the result of index join in correlated subqueries is wrong #25799
  • Fix a bug that the successfully committed optimistic transactions might report commit errors #10468
  • Fix the issue that an incorrect result is returned when using merge join on the SET type column #25669
  • Fix a bug that the index keys in a pessimistic transaction might be repeatedly committed #26359
  • Fix the risk of integer overflow when the optimizer is locating partitions #26227
  • Fix the issue that invalid values might be written when casting DATE to timestamp #26292
  • Fix the issue that the Coprocessor Cache metrics are not displayed on Grafana #26338
  • Fix the issue of annoying logs caused by telemetry #25760 #25785
  • Fix a bug on the query range of prefix index #26029
  • Fix the issue that concurrently truncating the same partition hangs DDL executions #26229
  • Fix the issue of duplicate ENUM items #25955
  • Fix a bug that the CTE iterator is not correctly closed #26112
  • Fix the issue that the LOAD DATA statement might abnormally import non-utf8 data #25979
  • Fix the panic issue that might occur when using the window function on the unsigned integer columns #25956
  • Fix the issue that TiDB might panic when resolving async commit locks #25778
  • Fix the issue that Stale Read is not fully compatible with the PREPARE statements #25800
  • Fix the issue that the ODBC-styled constant (for example, {d '2020-01-01'}) cannot be used as the expression #25531
  • Fix an error that occurs when running TiDB alone #25555

• TiKV

  • Fix the issue that the duration calculation might panic on certain platforms #10569
  • Fix the issue that Load Base Split mistakenly uses the unencoded keys of batch_get_command #10542
  • Fix the issue that changing the resolved-ts.advance-ts-interval configuration online cannot take effect immediately #10426
  • Fix the issue of follower metadata corruption in rare cases with more than 4 replicas #10225
  • Fix the panic issue that occurs when building a snapshot twice if encryption is enabled #9786 #10407
  • Fix the wrong tikv_raftstore_hibernated_peer_state metric #10330
  • Fix the wrong arguments type of the json_unquote() function in the coprocessor #10176
  • Fix a bug that the index keys in a pessimistic transaction might be repeatedly committed #10468
  • Fix the issue that the ReadIndex request returns stale result right after the leader is transferred #9351

• PD

  • Fix the issue the expected scheduling cannot be generated when the conflict occurs due to multiple schedulers running at the same time #3807 #3778
  • Fix the issue that the scheduler might appear again even if the scheduler is already deleted #2572

• TiFlash

  • Fix the potential panic issue that occurs when running table scan tasks
  • Fix a bug that TiFlash raises the error about duplicated region when handling DAQ requests
  • Fix the panic issue that occurs when the read load is heavy
  • Fix the potential panic issue that occurs when executing the DateFormat function
  • Fix the potential memory leak issue that occurs when executing MPP tasks
  • Fix the issue of unexpected results when executing the aggregation functions COUNT or COUNT DISTINCT
  • Fix a potential bug that TiFlash cannot restore data when deployed on multiple disks
  • Fix the issue that TiDB Dashboard cannot display the disk information of TiFlash correctly
  • Fix the potential panic issue that occurs when deconstructing SharedQueryBlockInputStream
  • Fix the potential panic issue that occurs when deconstructing MPPTask
  • Fix the potential issue of data inconsistency after synchronizing data via snapshot

• Tools

  • TiCDC

    • Fix the support for the new collation feature #2301
    • Fix the issue that an unsynchronized access to a shared map at runtime might cause panic #2300
    • Fix the potential DDL loss issue that occurs when the owner crashes while executing the DDL statement #2290
    • Fix the issue of trying to resolve locks in TiDB prematurely #2188
    • Fix a bug that might cause data loss if a TiCDC node is killed immediately after a table migration #2033
    • Fix the handling logic of changefeed update on --sort-dir and --start-ts #1921

  • Backup & Restore (BR)

    • Fix the issue that the size of the data to restore is incorrectly calculated #1270
    • Fix the issue of missed DDL events that occurs when restoring from cdclog #870

  • TiDB Lightning

    • Fix the issue that TiDB fails to parse the DECIMAL type data in Parquet files #1275
    • Fix the issue of integer overflow when calculating key intervals #1291 #1290