TiDB 5.0.3 Release Notes

Release date: July 2, 2021

TiDB version: 5.0.3

Compatibility Changes

• TiDB

  • After a v4.0 cluster is upgraded to v5.0 or a later version (dev or v5.1), the default value of the tidb_multi_statement_mode variable changes from WARN to OFF
  • TiDB is now compatible with MySQL 5.7's noop variable innodb_default_row_format. Setting this variable will have no effect. #23541

Feature Enhancements

• Tools

  • TiCDC

    • Add an HTTP API to get the changefeed information and the health information of the node #1955
    • Add the SASL/SCRAM support for the kafka sink #1942
    • Make TiCDC support --data-dir at the server level #2070

Improvements

• TiDB

  • Support pushing down the TopN operator to TiFlash #25162
  • Support pushing down the built-in function json_unquote() to TiKV #24415
  • Support removing the union branch from the dual table #25614
  • Support pushing down the built-in function replace() to TiFlash #25565
  • Support pushing down the built-in functions unix_timestamp(), concat(), year(), day(), datediff(), datesub(), and concat_ws() to TiFlash #25564
  • Optimize the aggregate operator's cost factor #25241
  • Support pushing down the Limit operator to TiFlash #25159
  • Support pushing down the built-in function str_to_date to TiFlash #25148
  • Allow the MPP outer join to choose the build table based on the table row count #25142
  • Support pushing down the built-in functions left(), right(), and abs() to TiFlash #25133
  • Support pushing down the Broadcast Cartesian join to TiFlash #25106
  • Support pushing down the Union All operator to TiFlash #25051
  • Support balancing the MPP query workload among different TiFlash nodes based on Regions #24724
  • Support invalidating stale Regions in the cache after the MPP query is executed #24432
  • Improve the MySQL compatibility of the built-in function str_to_date for the format specifiers %b/%M/%r/%T #25767

• TiKV

  • Limit the TiCDC sink's memory consumption #10305
  • Add the memory-bounded upper limit for the TiCDC old value cache #10313

• PD

  • Update TiDB Dashboard to v2021.06.15.1 #3798

• TiFlash

  • Support casting the STRING type to the DOUBLE type
  • Support the STR_TO_DATE() function
  • Optimize the non-joined data in right outer join using multiple threads
  • Support the Cartesian join
  • Support the LEFT() and RIGHT() functions
  • Support automatically invalidating stale Regions in MPP queries
  • Support the ABS() function

• Tools

  • TiCDC

    • Refine gRPC's reconnection logic and increase the KV client's throughput #1586 #1501 #1682 #1393 #1847 #1905 #1904
    • Make the sorter I/O errors more user-friendly

Bug Fixes

• TiDB

  • Fix the issue that an incorrect result is returned when using merge join on the SET type column #25669
  • Fix the data corruption issue in the IN expression's arguments #25591
  • Avoid the sessions of GC being affected by global variables #24976
  • Fix the panic issue that occurs when using limit in the window function queries #25344
  • Fix the wrong value returned when querying a partitioned table using Limit #24636
  • Fix the issue that IFNULL does not correctly take effect on the ENUM or SET type column #24944
  • Fix the wrong results caused by changing the count in the join subqueries to first_row #24865
  • Fix the query hang issue that occurs when ParallelApply is used under the TopN operator #24930
  • Fix the issue that more results than expected are returned when executing SQL statements using multi-column prefix indexes #24356
  • Fix the issue that the <=> operator cannot correctly take effect #24477
  • Fix the data race issue of the parallel Apply operator #23280
  • Fix the issue that the index out of range error is reported when sorting the IndexMerge results of the PartitionUnion operator #23919
  • Fix the issue that setting the tidb_snapshot variable to an unexpectedly large value might damage the transaction isolation #25680
  • Fix the issue that the ODBC-styled constant (for example, {d '2020-01-01'}) cannot be used as the expression #25531
  • Fix the issue that SELECT DISTINCT converted to Batch Get causes incorrect results #25320
  • Fix the issue that backing off queries from TiFlash to TiKV cannot be triggered #23665 #24421
  • Fix the index-out-of-range error that occurs when checking only_full_group_by #23839)
  • Fix the issue that the result of index join in correlated subqueries is wrong #25799

• TiKV

  • Fix the wrong tikv_raftstore_hibernated_peer_state metric #10330
  • Fix the wrong arguments type of the json_unquote() function in the coprocessor #10176
  • Skip clearing callback during graceful shutdown to avoid breaking ACID in some cases #10353 #10307
  • Fix a bug that the read index is shared for replica reads on a Leader #10347
  • Fix the wrong function that casts DOUBLE to DOUBLE #25200

• PD

  • Fix the data race issue that occurs when loading TTL configurations after the scheduler is started #3771
  • Fix a bug that the is_learner field of the TIKV_REGION_PEERS table in TiDB is incorrect #3372 #24293
  • Fix the issue that when all TiKV nodes in a zone are offline or down, PD does not schedule replicas to other zones #3705
  • Fix the issue that PD might get panic after the scatter Region scheduler is added #3762

• TiFlash

  • Fix the issue that TiFlash keeps restarting because of the split failure
  • Fix the potential issue that TiFlash cannot delete the delta data
  • Fix a bug that TiFlash adds wrong padding for non-binary characters in the CAST function
  • Fix the issue of incorrect results when handling aggregation queries with complex GROUP BY columns
  • Fix the TiFlash panic issue that occurs under heavy write pressure
  • Fix the panic that occurs when the right jon key is not nullalbe and the left join key is nullable
  • Fix the potential issue that the read-index requests take a long time
  • Fix the panic issue that occurs when the read load is heavy
  • Fix the panic issue that might occur when the Date_Format function is called with the STRING type argument and NULL values

• Tools

  • TiCDC

    • Fix the issue that TiCDC owner exits when refreshing the checkpoint #1902
    • Fix a bug that some MySQL connection might leak after MySQL sink meets the error and pauses #1946
    • Fix the panic issue that occurs when TiCDC fails to read /proc/meminfo #2024
    • Reduce TiCDC's runtime memory consumption #2012 #1958
    • Fix a bug that might cause TiCDC server panic due to the late calculation of resolved ts #1576
    • Fix the potential deadlock issue for the processor #2142

  • Backup & Restore (BR)

    • Fix a bug that all system tables are filtered during restore #1197 #1201
    • Fix the issue that Backup & Restore reports the error of "file already exists" when TDE is enabled during the restore #1179

  • TiDB Lightning

    • Fix the TiDB Lightning panic issue for some special data #1213
    • 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 #1186
    • Fix the issue that TiDB fails to parse the DECIMAL type data in Parquet files #1277