TiDB 5.0.1 Release Notes

Release date: April 24, 2021

TiDB version: 5.0.1

Compatibility change

• The default value of the committer-concurrency configuration item is changed from 16 to 128.

Improvements

• TiDB

  • Support the built-in function VITESS_HASH() #23915

• TiKV

  • Use zstd to compress the Region snapshot #10005

• PD

  • Modify the Region score calculator to better satisfy isomerous stores #3605
  • Avoid unexpected statistics after adding the scatter region scheduler #3602

• Tools

  • Backup & Restore (BR)

    • Remove some misleading information from the summary log #1009

Bug Fixes

• TiDB

  • Fix the issue that the execution result of project elimination might be wrong when the projection result is empty #24093
  • Fix the issue of wrong query results when a column contains NULL values in some cases #24063
  • Forbid generating MPP plans when the scan contains virtual columns #24058
  • Fix the wrong reuse of PointGet and TableDual in Plan Cache #24043
  • Fix the error that occurs when the optimizer builds the IndexMerge plan for clustered indexes #24042
  • Fix the type inference of the BIT-type errors #24027
  • Fix the issue that some optimizer hints do not take effect when the PointGet operator exists #23685
  • Fix the issue that DDL operations might fail when rolling back due to an error #24080
  • Fix the issue that the index range of the binary literal constant is incorrectly built #24041
  • Fix the potential wrong results of the IN clause in some cases #24023
  • Fix the wrong results of some string functions #23879
  • Users now need both INSERT and DELETE privileges on a table to perform REPLACE operations #23939
  • Fix the performance regression when executing the point query #24070
  • Fix the wrong TableDual plans caused by incorrectly comparing binaries and bytes #23918

• TiKV

  • Fix the issue that the coprocessor fails to properly handle the signed or unsigned integer types in the IN expression #10018
  • Fix the issue of many empty Regions after batch ingesting SST files #10015
  • Fix the potential panic that occurs when the input of cast_string_as_time is invalid UTF-8 bytes #9995
  • Fix a bug that TiKV cannot start up after the file dictionary file is damaged #9992

• TiFlash

  • Fix the issue that the storage engine fails to remove the data of some ranges
  • Fix the issue of incorrect results when casting the time type to the integer type
  • Fix a bug that the receiver cannot find corresponding tasks within 10 seconds
  • Fix the issue that there might be invalid iterators in cancelMPPQuery
  • Fix a bug that the behavior of the bitwise operator is different from that of TiDB
  • Fix the alert issue caused by overlapping ranges when using the prefix key
  • Fix the issue of incorrect results when casting the string type to the integer type
  • Fix the issue that consecutive and fast writes might make TiFlash out of memory
  • Fix the issue that duplicated column names will make TiFlash raise errors
  • Fix the issue that TiFlash fails to parse MPP plans
  • Fix the potential issue that the exception of null pointer might be raised during the table GC
  • Fix the TiFlash panic issue that occurs when writing data to dropped tables
  • Fix the issue that TiFlash might panic during BR restore

• Tools

  • TiDB Lightning

    • Fix the issue of the inaccurate table count in the progress log during the import #1005

  • Backup & Restore (BR)

    • Fix a bug that the actual backup speed exceeds the --ratelimit limit #1026
    • Fix the issue of backup interruption caused by the failure of a few TiKV nodes #1019
    • Fix the issue of the inaccurate table count in the progress log during TiDB Lightning's import #1005

  • TiCDC

    • Fix the concurrency issue in Unified Sorter and filter the unhelpful error messages #1678
    • Fix a bug that the creation of redundant directories might interrupt the replication with MinIO #1672
    • Set the default value of the explicit_defaults_for_timestamp session variable to ON to make the MySQL 5.7 downstream keep the same behavior with the upstream TiDB #1659
    • Fix the issue that the incorrect handling of io.EOF might cause replication interruption #1648
    • Correct the TiKV CDC endpoint CPU metric in the TiCDC dashboard #1645
    • Increase defaultBufferChanSize to avoid replication blocking in some cases #1632