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TiDB 5.1.2 Release Notes
TiDB 5.1.2 was released on September 27, 2021. The release includes compatibility changes, improvements, bug fixes, and updates to various tools such as TiCDC, TiKV, PD, TiFlash, BR, Dumpling, and TiCDC. The release addresses numerous bug fixes and improvements to enhance performance and stability.

TiDB 5.1.2 Release Notes

Release Date: September 27, 2021

TiDB version: 5.1.2

Compatibility changes

  • TiDB

    • The following bug fixes change execution results, which might cause upgrade incompatibilities:

      • Fix the issue that greatest(datetime) union null returns empty string #26532
      • Fix the issue that the having clause might not work correctly #26496
      • Fix the wrong execution results that occur when the collations around the between expression are different #27146
      • Fix the wrong execution results that occur when the column in the group_concat function has a non-bin collation #27429
      • Fix an issue that using a count(distinct) expression on multiple columns returns wrong result when the new collation is enabled #27091
      • Fix the result wrong that occurs when the argument of the extract function is a negative duration #27236
      • Fix the issue that inserting an invalid date does not report an error when the SQL_MODE is 'STRICT_TRANS_TABLES' #26762
      • Fix the issue that using an invalid default date does not report an error when the SQL_MODE is 'NO_ZERO_IN_DATE' #26766

  • Tools

    • TiCDC

      • Set the compatible version from 5.1.0-alpha to 5.2.0-alpha #2659

Improvements

  • TiDB

    • Trigger auto-analyze by histogram row count and increase the accuracy of this trigger action #24237

  • TiKV

    • Support dynamically modifying TiCDC configurations #10645
    • Reduce the size of Resolved TS message to save network bandwidth #2448
    • Limit the counts of peer stats in the heartbeat message reported by a single store #10621

  • PD

    • Allow empty Regions to be scheduled and use a separate tolerance configuration in scatter range scheduler #4117
    • Improve the performance of synchronizing Region information between PDs #3933
    • Support dynamically adjusting the retry limit of a store based on the generated operator #3744

  • TiFlash

    • Support the DATE() function
    • Add Grafana panels for write throughput per instance
    • Optimize the performance of the leader-read process
    • Accelerate the process of canceling MPP tasks

  • Tools

    • TiCDC

      • Optimize memory management when the Unified Sorter is using memory to sort data #2553
      • Optimize workerpool for fewer goroutines when concurrency is high #2211
      • Reduce goroutine usage when a table's Region transfer away from a TiKV node #2284
      • Add a global gRPC connection pool and share gRPC connections among KV clients #2534
      • Prohibit operating TiCDC clusters across major and minor versions #2599

    • Dumpling

      • Support backing up MySQL-compatible databases that do not support START TRANSACTION ... WITH CONSISTENT SNAPSHOT and SHOW CREATE TABLE #309

Bug fixes

  • TiDB

    • Fix the potential wrong results of index hash join when the hash column is the ENUM type #27893
    • Fix a batch client bug that recycle idle connection might block sending requests in some rare cases #27678
    • Fix the issue that the overflow check of the FLOAT64 type is different with that of MySQL #23897
    • Fix the issue that TiDB returns an unknow error while it should return the pd is timeout error #26147
    • Fix the wrong character set and collation for the case when expression #26662
    • Fix the potential can not found column in Schema column error for MPP queries #28148
    • Fix a bug that TiDB might panic when TiFlash is shutting down #28096
    • Fix the issue of wrong range caused by using enum like 'x%' #27130
    • Fix the Common Table Expression (CTE) dead lock issue when used with IndexLookupJoin #27410
    • Fix a bug that retryable deadlocks are incorrectly recorded into the INFORMATION_SCHEMA.DEADLOCKS table #27400
    • Fix the issue that the TABLESAMPLE query result from partitioned tables is not sorted as expected #27349
    • Remove the unused /debug/sub-optimal-plan HTTP API #27265
    • Fix a bug that the query might return wrong results when the hash partitioned table deals with unsigned data #26569
    • Fix a bug that creating partition fails if NO_UNSIGNED_SUBTRACTION is set #26765
    • Fix the issue that the distinct flag is missing when Apply is converted to Join #26958
    • Set a block duration for the newly recovered TiFlash node to avoid blocking queries during this time #26897
    • Fix a bug that might occur when the CTE is referenced more than once #26212
    • Fix a CTE bug when MergeJoin is used #25474
    • Fix a bug that the SELECT FOR UPDATE statement does not correctly lock the data when a normal table joins a partitioned table #26251
    • Fix the issue that the SELECT FOR UPDATE statement returns an error when a normal table joins a partitioned table #26250
    • Fix the issue that PointGet does not use the lite version of resolving lock #26562

  • TiKV

    • Fix a panic issue that occurs after TiKV is upgraded from v3.x to later versions #10902
    • Fix the potential disk full issue caused by corrupted snapshot files #10813
    • Make the slow log of TiKV coprocessor only consider the time spent on processing requests #10841
    • Drop log instead of blocking threads when the slogger thread is overloaded and the queue is filled up #10841
    • Fix a panic issue that occurs when processing Coprocessor requests times out #10852
    • Fix the TiKV panic issue that occurs when upgrading from a pre-5.0 version with Titan enabled #10842
    • Fix the issue that TiKV of a newer version cannot be rolled back to v5.0.x #10842
    • Fix the issue that TiKV might delete files before ingesting data to RocksDB #10438
    • Fix the parsing failure caused by the left pessimistic locks #26404

  • PD

    • Fix the issue that PD does not fix the down peers in time #4077
    • Fix the issue that the replica count of the default placement rules stays constant after replication.max-replicas is updated #3886
    • Fix a bug that PD might panic when scaling out TiKV #3868
    • Fix a bug that the hot Region scheduler cannot work when the cluster has the evict leader scheduler #3697

  • TiFlash

    • Fix the issue of unexpected results when TiFlash fails to establish MPP connections
    • Fix the potential issue of data inconsistency that occurs when TiFlash is deployed on multiple disks
    • Fix a bug that MPP queries get wrong results when TiFlash server is under high load
    • Fix a potential bug that MPP queries hang forever
    • Fix the panic issue when operating store initialization and DDL simultaneously
    • Fix a bug of incorrect results that occurs when queries contain filters like CONSTANT, <, <=, >, >=, or COLUMN
    • Fix the potential panic issue when Snapshot is applied simultaneously with multiple DDL operations
    • Fix the issue that the store size in metrics is inaccurate under heavy writing
    • Fix the potential issue that TiFlash cannot garbage-collect the delta data after running for a long time
    • Fix the issue of wrong results when the new collation is enabled
    • Fix the potential panic issue that occurs when resolving locks
    • Fix a potential bug that metrics display wrong values

  • Tools

    • Backup & Restore (BR)

      • Fix the issue that the average speed is not accurate during data backup and restore #1405

    • Dumpling

      • Fix the issue that Dumpling is pending when show table status returns incorrect results in some MySQL versions (8.0.3 and 8.0.23) #322
      • Fix the CLI compatibility issue with 4.0.x clusters on the default sort-engine option #2373

    • TiCDC

      • Fix a bug that the JSON encoding might cause panic when processing a string type value that is string or []byte #2758
      • Reduce gRPC window size to avoid OOM #2673
      • Fix a gRPC keepalive error under high memory pressure #2202
      • Fix a bug that an unsigned tinyint causes TiCDC to panic #2648
      • Fix an empty value issue in TiCDC Open Protocol. An empty value is no longer output when there is no change in one transaction. #2612
      • Fix a bug in DDL handling during manual restarts #2603
      • Fix the issue that EtcdWorker's snapshot isolation might be wrongly violated when managing the metadata #2559
      • Fix a bug that multiple processors might write data to the same table when TiCDC is rescheduling the table #2230
      • Fix a bug that changefeed might be reset unexpectedly when TiCDC gets the ErrSchemaStorageTableMiss error #2422
      • Fix a bug that changefeed cannot be removed when TiCDC gets the ErrGCTTLExceeded error #2391
      • Fix a bug that TiCDC fails to synchronize large tables to cdclog #1259 #2424