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TiDB 4.0.5 Release Notes
TiDB 4.0.5 was released on August 31, 2020. The new version includes compatibility changes, new features, improvements, bug fixes, and updates to TiKV, TiFlash, Tools, PD, and TiDB Lightning. Some notable changes include support for the unified log format with TiDB, optimization of performance, bug fixes for various issues, and support for encryption at rest for data storage in TiFlash.

TiDB 4.0.5 Release Notes

Release date: August 31, 2020

TiDB version: 4.0.5

Compatibility Changes

  • TiDB

    • Change drop partition and truncate partition's job arguments to support the ID array of multiple partitions #18930
    • Add the delete-only state for checking add partition replicas #18865

New Features

  • TiKV

    • Define error code for errors #8387

  • TiFlash

    • Support the unified log format with TiDB

  • Tools

    • TiCDC

      • Support Kafka SSL connection #764
      • Support outputting the old value #708
      • Add the column flags #796
      • Support outputting the DDL statements and table schema of the previous version #799

Improvements

  • TiDB

    • Optimize the performance of DecodePlan for big union queries #18941
    • Reduce the number of GC lock scans when the Region cache miss error occurs #18876
    • Ease the impact of statistical feedback on cluster performance #18772
    • Support canceling operations before the RPC response is returned #18580
    • Add the HTTP API to generate the TiDB metric profile #18531
    • Support scattering partitioned tables #17863
    • Add detailed memory usage of each instance in Grafana #18679
    • Show the detailed runtime information of the BatchPointGet operator in the result of EXPLAIN #18892
    • Show the detailed runtime information of the PointGet operator in the result of EXPLAIN #18817
    • Warn the potential deadlock for Consume in remove() #18395
    • Refine the behaviors of StrToInt and StrToFloat and support converting JSON to the date, time, and timestamp types #18159
    • Support limiting the memory usage of the TableReader operator #18392
    • Avoid too many times of backoff when retrying the batch cop request #18999
    • Improve compatibility for ALTER TABLE algorithms #19270
    • Make the single partitioned table support IndexJoin on the inner side #19151
    • Support searching the log file even when the log includes invalid lines #18579

  • PD

    • Support scattering Regions in stores with special engines (such as TiFlash) #2706
    • Support the Region HTTP API to prioritize Region scheduling of a given key range #2687
    • Improve the leader distribution after Region scattering #2684
    • Add more tests and logs for the TSO request #2678
    • Avoid invalid cache updates after the leader of a Region has changed #2672
    • Add an option to allow store.GetLimit to return the tombstone stores #2743
    • Support synchronizing the Region leader change between the PD leader and followers #2795
    • Add commands for querying the GC safepoint service #2797
    • Replace the region.Clone call in filters to improve performance #2801
    • Add an option to disable updating Region flow cache to improve the performance of the large cluster #2848

  • TiFlash

    • Add more Grafana panels to display metrics of CPU, I/O, RAM usages and metrics of the storage engine
    • Reduce I/O operations by optimizing the processing logic of Raft logs
    • Accelerate Region scheduling for the blocked add partition DDL statement
    • Optimize compactions of delta data in DeltaTree to reduce read and write amplification
    • Optimize the performance of applying Region snapshots by preprocessing the snapshots using multiple threads
    • Optimize the number of opening file descriptors when the read load of TiFlash is low to reduce system resource consumption
    • Optimize the number of unnecessary small files created when TiFlash restarts
    • Support encryption at rest for data storage
    • Support TLS for data transfer

  • Tools

    • TiCDC

      • Lower the frequency of getting TSO #801

    • Backup & Restore (BR)

      • Optimize some logs #428

    • Dumpling

      • Release FTWRL after connections are created to reduce the lock time for MySQL #121

    • TiDB Lightning

      • Optimize some logs #352

Bug Fixes

  • TiDB

    • Fix the should ensure all columns have the same length error that occurs because the ErrTruncate/Overflow error is incorrectly handled in the builtinCastRealAsDecimalSig function #18967
    • Fix the issue that the pre_split_regions table option does not work in the partitioned table #18837
    • Fix the issue that might cause a large transaction to be terminated prematurely #18813
    • Fix the issue that using the collation functions get wrong query results #18735
    • Fix the bug that the getAutoIncrementID() function does not consider the tidb_snapshot session variable, which might cause the dumper tool to fail with the table not exist error #18692
    • Fix the unknown column error for SQL statement like select a from t having t.a #18434
    • Fix the panic issue that writing the 64-bit unsigned type into the hash partitioned table causes overflow and gets an unexpected negative number when the partition key is the integer type #18186
    • Fix the wrong behavior of the char function #18122
    • Fix the issue that the ADMIN REPAIR TABLE statement cannot parse integer in the expressions on the range partition #17988
    • Fix the wrong behavior of the SET CHARSET statement #17289
    • Fix the bug caused by the wrong collation setting which leads to the wrong result of the collation function #17231
    • Fix the issue that STR_TO_DATE's handling of the format tokens '%r', '%h' is inconsistent with that of MySQL #18727
    • Fix issues that the TiDB version information is inconsistent with that of PD/TiKV in the cluster_info table #18413
    • Fix the existent checks for pessimistic transactions #19004
    • Fix the issue that executing union select for update might cause concurrent race #19006
    • Fix the wrong query result when apply has a child of the PointGet operator #19046
    • Fix the incorrect result that occurs when IndexLookUp is in the inner side of the Apply operator #19496
    • Fix the incorrect result of anti-semi-join queries #19472
    • Fix the incorrect result caused by the mistaken usage of BatchPointGet #19456
    • Fix the incorrect result that occurs when UnionScan is in the inner side of the Apply operator #19496
    • Fix the panic caused by using the EXECUTE statement to print an expensive query log #17419
    • Fix the index join error when the join key is ENUM or SET #19235
    • Fix the issue that the query range cannot be built when the NULL value exists on the index column #19358
    • Fix the data race issue caused by updating the global configuration #17964
    • Fix the panic issue occurs when modifying the character set in an uppercase schema #19286
    • Fix an unexpected error caused by changing the temporary directory during the disk spill action #18970
    • Fix the wrong hash key for the decimal type #19131
    • Fix the issue that the PointGet and BatchPointGet operators do not consider the partition selection syntax and get incorrect results #19141
    • Fix the incorrect results when using the Apply operator together with the UnionScan operator #19104
    • Fix the bug that causes the indexed virtual generated column to return wrong value #17989
    • Add the lock for runtime statistics to fix a panic caused by concurrent execution #18983

  • TiKV

    • Speed up leader election when Hibernate Region is enabled #8292
    • Fix the memory leak issue during scheduling #8357
    • Add the hibernate-timeout configuration item to prevent the leader from becoming hibernate too fast #8208

  • PD

    • Fix the bug that the TSO request might fail at the time of leader change #2666
    • Fix the issue that sometimes Region replicas cannot be scheduled to the optimal state when placement rules are enabled #2720
    • Fix the issue that Balance Leader does not work when placement rules are enabled #2726
    • Fix the issue that unhealthy stores are not filtered from store load statistics #2805

  • TiFlash

    • Fix the issue that TiFlash cannot start normally after upgrading from an earlier version if the name of the database or table contains special characters
    • Fix the issue that the TiFlash process cannot exit if any exceptions are thrown during initialization

  • Tools

    • Backup & Restore (BR)

      • Fix the issue of duplicated calculation of total KV and total bytes in the backup summary log #472
      • Fix the issue that the import mode does not work in the first 5 minutes after switching to this mode #473

    • Dumpling

      • Fix the issue that FTWRL lock is not released in time #128

    • TiCDC

      • Fix the issue that the failed changefeed cannot be removed #782
      • Fix invalid delete events by selecting one unique index as the handle index #787
      • Fix the bug that GC safepoint is forwarded beyond the checkpoint of stopped changefeed #797
      • Fix the bug that the network I/O waiting blocks tasks to exit #825
      • Fix the bug that some unnecessary data might be mistakenly replicated to the downstream #743

    • TiDB Lightning

      • Fix the syntax error on empty binary/hex literals when using TiDB backend #357