TiDB 4.0 GA Release Notes

Release date: May 28, 2020

TiDB version: 4.0.0

Compatibility Changes

TiDB
- Optimize the error message of the large-sized transactions for easier troubleshooting #17219
TiCDC
- Optimize the structure of the Changefeed configuration file to improve usability #588
- Add the ignore-txn-start-ts configuration item, and change the condition from commit_ts to start_ts during transactions filtering #589

Important Bug Fixes

TiKV
- Fix the DefaultNotFound error that occurs when backing up using Backup & Restore (BR) #7937
- Fix system panics caused by the out-of-order ReadIndex packages #7930
- Fix system panics caused by incorrectly removing snapshot files after TiKV is restarted #7927
TiFlash
- Fix the possible data loss issue that occurs when the system panics because of incorrect processing logic of Raft Admin Command

New Features

TiDB
- Add the committer-concurrency configuration item to control the number of goroutines in the retry-commit phase #16849
- Support the show table partition regions syntax #17294
- Add the tmp-storage-quota configuration item to limit the temporary disk space used by the TiDB server #15700
- Support checking whether the partitioned table uses a unique prefix index when creating and changing tables #17213
- Support the insert/replace into tbl_name partition(partition_name_list) statement #17313
- Support checking the value of collations when using the Distinct function #17240
- Support the is null filter condition during the Hash partition pruning #17310
- Support admin check index, admin cleanup index, and admin recover index in partitioned tables #17392 #17405 #17317
- Support range partition pruning for the in expressions #17320
TiFlash
- Support filtering out the data corresponding to the qualified TSO through the min commit ts value of the Lock CF when the Learner reads the data
- Add the feature that the system explicitly reports an error to avoid incorrect calculation results when the value of TIMESTAMP type is less than 1970-01-01 00:00:00
- Support using flags in regular expressions when searching logs
TiKV
- Support collation rules of ascii_bin and latin1_bin encoding #7919
PD
- Support specifying the reverse proxy resource prefix for built-in TiDB Dashboard #2457
- Support returning the pending peer and down peer information in interfaces of the PD client Region #2443
- Add monitoring items such as Direction of hotspot move leader, Direction of hotspot move peer, and Hot cache read entry number #2448
Tools
- Backup & Restore (BR)
  - Support the backup and restore of Sequence and View #242
- TiCDC
  - Support checking the validity of Sink URI when creating Changefeed #561
  - Support checking whether the PD and TiKV versions meet the system requirements during system startup #570
  - Support scheduling multiple tables in the same scheduling task generation cycle #572
  - Add information about node roles in HTTP API #591

Bug Fixes

TiDB
- Fix the issue of unexpected timeouts when sending and receiving messages by disabling TiDB to send batch commands to TiFlash #17307
- Fix the issue of incorrectly distinguishing signed and unsigned integers during partition pruning, which improves performance #17230
- Fix the issue of upgrade failure from v3.1.1 to v4.0 because of the incompatible mysql.user table #17300
- Fix the issue of incorrect selection of the partition in the update statement #17305
- Fix system panics when receiving an unknown error message from TiKV #17380
- Fix system panics caused by incorrect processing logic when creating the table that is key partitioned #17242
- Fix the issue that the wrong Index Merge Join plan is selected because of incorrect optimizer processing logic #17365
- Fix the issue of inaccurate duration monitoring metric of the SELECT statement in Grafana #16561
- Fix the issue that the GC worker is blocked when the system error occurs #16915
- Fix the issue that the UNIQUE constraint on a boolean column results in an incorrect result in a comparison #17306
- Fix system panics caused by incorrect processing logic when tidb_opt_agg_push_down is enabled and the aggregation function pushes down the partitioned table #17328
- Fix the issue of accessing failed TiKV nodes in some cases #17342
- Fix the issue that the isolation-read configuration item in tidb.toml does not take effect #17322
- Fix the issue of incorrect order of output results due to incorrect processing logic when hint is used to enforce the stream aggregation #17347
- Fix the behavior that insert processes DIV under different SQL_MODE #17314
TiFlash
- Fix the issue that the matching behavior of regular expressions in the search log feature is inconsistent with other components
- Fix the issue of excessive restart time when nodes write large amounts of data by disabling the delay processing optimization of Raft Compact Log Command by default
- Fix the issue that the system fails to start because TiDB incorrectly processes the DROP DATABASE statement in some scenarios
- Fix the issue that the method of collecting CPU information in Server_info is different from that in other components
- Fix the issue that the error Too Many Pings is reported when the Query statement is executed if batch coprocessor is enabled
- Fix the issue that Dashboard fails to display the correct deploy path information because TiFlash does not report the related information
TiKV
- Fix the DefaultNotFound error that occurs when backing up using BR #7937
- Fix system panics caused by out-of-order ReadIndex packets #7930
- Fix the issue that an unexpected error is returned because the read request callback function is not called #7921
- Fix system panics caused by incorrectly removing snapshot files when TiKV is restarted #7927
- Fix the issue that the master key cannot be rotated due to incorrect processing logic in storage encryption #7898
- Fix the issue that the received lock cf file of the snapshot is not encrypted when the storage encryption is enabled #7922
PD
- Fix the 404 error when deleting evict-leader-scheduler or grant-leader-scheduler using pd-ctl #2446
- Fix the issue that the presplit feature might not work properly when the TiFlash replica exists #2447
Tools
- Backup & Restore (BR)
  - Fix the issue that the data restoration fails due to network issues when BR restores data from cloud storage #298
- TiCDC
  - Fix system panics caused by data race #565 #566
  - Fix resource leaks or system blockages caused by incorrect processing logic #574 #586
  - Fix the issue that the command line gets stuck because CLI cannot connect to PD #579