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TiDB 4.0.15 Release Notes
Release Date: September 27, 2021
TiDB version: 4.0.15
Compatibility changes
TiDB
- Fix the issue that executing
SHOW VARIABLES
in a new session is slow. This fix reverts some changes made in #21045 and might cause compatibility issues. #24326
- 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 result wrong that occurs when the argument of the
extract
function is a negative duration #27236 - Fix the wrong execution results that occur when the column in the
group_concat
function has a non-bin collation #27429 - Fix the issue that column information is missed when converting the
Apply
operator toJoin
#27233 - Fix the issue of unexpected behavior when casting the invalid string to
DATE
#26762 - Fix a bug that the
count distinct
result on multiple columns is wrong when the new collation is enabled #27091
- Fix the issue that
- Fix the issue that executing
Feature enhancement
TiKV
- Support changing TiCDC configurations dynamically #10645
Improvements
TiDB
- Trigger auto-analyze based on the histogram row count #24237
TiKV
- Handle read ready and write ready separately to reduce read latency #10475
- The slow log of TiKV coprocessor only considers 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
- Reduce the size of Resolved TS messages to save network bandwidth #2448
PD
- Improve the performance of synchronizing Region information between PDs #3932
Tools
Backup & Restore (BR)
- Split and scatter Regions concurrently to improve restore speed #1363
- Retry BR tasks when encountering the PD request error or the TiKV I/O timeout error #27787
- Reduce empty Regions when restoring many small tables to avoid affecting cluster operations after the restore #1374
- Perform the
rebase auto id
operation while creating tables, which saves the separaterebase auto id
DDL operation and speeds up restore #1424
Dumpling
- Filter the skipped databases before getting the table information to improve the filtering efficiency of
SHOW TABLE STATUS
#337 - Use
SHOW FULL TABLES
to get table information for tables to be exported, becauseSHOW TABLE STATUS
cannot work properly in some MySQL versions #322 - Support backing up MySQL-compatible databases that do not support the
START TRANSACTION ... WITH CONSISTENT SNAPSHOT
or theSHOW CREATE TABLE
syntax #309 - Refine the Dumpling warning log to avoid the misleading information that a dump fails #340
- Filter the skipped databases before getting the table information to improve the filtering efficiency of
TiDB Lightning
- Support importing data into tables that have expression index or the index that depends on virtual generated columns #1404
TiCDC
- Always pulls old values from TiKV internally to improve usability #2397
- Reduce the goroutine usage when a table's Regions are all transferred away from a TiKV node #2284
- Optimize workerpool for fewer goroutines when concurrency is high #2211
- Execute DDL statements asynchronously to avoid affecting other changefeeds #2295
- Add a global gRPC connection pool and share gRPC connections among KV clients #2531
- Fail fast for unrecoverable DML errors #1724
- Optimize memory management when the Unified Sorter is using memory to sort data #2553
- Add Prometheus metrics for DDL executions #2595 #2669
- Prohibit operating TiCDC clusters across major or minor versions #2601
- Remove
file sorter
#2325 - Clean up changefeed metrics when a changefeed is removed, and clean up processor metrics when a processor exits #2156
- Optimize the lock-resolving algorithm after a Region is initialized #2188
Bug fixes
TiDB
Fix a bug that collation is incorrectly set for binary literals when building ranges #23672
Fix the "index out of range" error that occurs when a query includes both
GROUP BY
andUNION
#26553Fix the issue that TiDB might fail to send requests if TiKV has tombstone stores #23676 #24648
Remove the undocumented
/debug/sub-optimal-plan
HTTP API #27264Fix the issue of wrong character set and collation for the
case when
expression #26662
TiKV
- Fix the issue that BR reports the "file already exists" error when TDE is enabled during data restore #1179
- Fix the potential disk full issue caused by corrupted snapshot files #10813
- Fix the issue that TiKV deletes stale Regions too frequently #10680
- Fix the issue that TiKV frequently reconnects the PD client #9690
- Check stale file information from the encryption file dictionary #9115
PD
TiFlash
- Fix the potential issue of data inconsistency that occurs when TiFlash is deployed on multiple disks
- Fix a bug of incorrect results that occurs when queries contain filters like
CONSTANT
,<
,<=
,>
,>=
, orCOLUMN
- Fix the issue that the store size in metrics is inaccurate under heavy writing
- Fix a potential bug that TiFlash cannot restore data when deployed on multiple disks
- Fix the potential issue that TiFlash cannot garbage-collect the delta data after running for a long time
Tools
Backup & Restore (BR)
- Fix a bug that the average speed is inaccurately calculated for backup and restore #1405
TiCDC
- Fix the
ErrSchemaStorageTableMiss
error that occurs when the DDL Job duplication is encountered in the integrated test #2422 - Fix a bug that a changefeed cannot be removed if the
ErrGCTTLExceeded
error occurs #2391 - Fix the issue that outdated capture might appear in the output of the
capture list
command #2388 - Fix the deadlock issue in the TiCDC processor #2017
- Fix a data inconsistency issue that occurs because multiple processors might write data to the same table when this table is being re-scheduled #2230
- Fix a bug that the
EtcdWorker
snapshot isolation is violated in metadata management #2557 - Fix the issue that the changefeed cannot be stopped due to the DDL sink error #2552
- Fix the issue of TiCDC Open Protocol: TiCDC outputs an empty value when there is no change in a transaction #2612
- Fix a bug that causes TiCDC to panic on the unsigned
TINYINT
type #2648 - Decrease the gRPC window size to avoid the OOM that occurs when TiCDC captures too many Regions #2202
- Fix the OOM issue that occurs when TiCDC captures too many Regions #2673
- Fix the issue of process panic that occurs when encoding the data types such as
mysql.TypeString, mysql.TypeVarString, mysql.TypeVarchar
into JSON #2758 - Fix the a memory leak issue that might occur when creating a new changefeed #2389
- Fix a bug that DDL handling fails when a changefeed starts at the finish TS of a schema change #2603
- Fix the issue of potential DDL loss when the owner crashes when executing DDL statements #1260
- Fix the issue of insecure concurrent access to the map in
SinkManager
#2298
- Fix the
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