TiDB 7.5.5 Release Notes

Release date: December 31, 2024

TiDB version: 7.5.5

Quick access: Quick start | Production deployment

Compatibility changes

• Add a new system variable tidb_ddl_reorg_max_write_speed to limit the maximum speed of the ingest phase when adding indexes #57156 @CbcWestwolf
• Change the default value of the TiKV configuration item raft-client-queue-size from 8192 to 16384 #17101 @Connor1996

Improvements

• TiDB

  • Adjust estimation results from 0 to 1 for equality conditions that do not hit TopN when statistics are entirely composed of TopN and the modified row count in the corresponding table statistics is non-zero #47400 @terry1purcell

• TiKV

  • Fix the issue that when Raft and RocksDB are deployed on different disks, the slow disk detection does not work for the disk where RocksDB is located #17884 @LykxSassinator
  • Add slow logs for peer and store messages #16600 @Connor1996
  • Optimize the jittery access delay when restarting TiKV due to waiting for the log to be applied, improving the stability of TiKV #15874 @LykxSassinator

• TiFlash

  • Mitigate the issue that TiFlash might panic due to updating certificates after TLS is enabled #8535 @windtalker
  • Improve the garbage collection speed of outdated data in the background for tables with clustered indexes #9529 @JaySon-Huang
  • Optimize the retry strategy for TiFlash compute nodes in the disaggregated storage and compute architecture to handle exceptions when downloading files from Amazon S3 #9695 @JinheLin

• Tools

  • Backup & Restore (BR)

    • Reduce unnecessary log printing during backup #55902 @Leavrth

  • TiDB Data Migration (DM)

    • Lower the log level for unrecognized MariaDB binlog events #10204 @dveeden

Bug fixes

• TiDB

  • Fix the issue that TiDB cannot resume Reorg DDL tasks from the previous progress after the DDL owner node is switched #56506 @tangenta
  • Fix the issue that invalid NULL values can be inserted in non-strict mode (sql_mode = '') #56381 @joechenrh
  • Fix the issue that the data in the Stats Healthy Distribution panel of Grafana might be incorrect #57176 @hawkingrei
  • Fix the issue of illegal memory access that might occur when a Common Table Expression (CTE) has multiple data consumers and one consumer exits without reading any data #55881 @windtalker
  • Fix the issue that existing TTL tasks are executed unexpectedly frequently in a cluster that is upgraded from v6.5 to v7.5 or later #56539 @lcwangchao
  • Fix the issue that TTL tasks are not canceled after the tidb_ttl_job_enable variable is disabled #57404 @YangKeao
  • Fix the issue that the query latency of stale reads increases, caused by information schema cache misses #53428 @crazycs520
  • Fix the issue that stale read does not strictly verify the timestamp of the read operation, resulting in a small probability of affecting the consistency of the transaction when an offset exists between the TSO and the real physical time #56809 @MyonKeminta
  • Fix the issue that the AUTO_INCREMENT field is not correctly set after importing data using the IMPORT INTO statement #56476 @D3Hunter
  • Fix the issue that two DDL Owners might exist at the same time #54689 @joccau
  • Fix the issue that TTL might fail if TiKV is not selected as the storage engine #56402 @YangKeao
  • Fix the issue that TiDB does not check the index length limitation when executing ADD INDEX #56930 @fzzf678
  • Fix the issue that when canceling a TTL task, the corresponding SQL is not killed forcibly #56511 @lcwangchao
  • Fix the issue that execution plan bindings cannot be created for the multi-table DELETE statement with aliases #56726 @hawkingrei
  • Fix the issue that when using ANALYZE to collect statistics for a table, if the table contains expression indexes of virtually generated columns, the execution reports an error #57079 @hawkingrei
  • Fix the issue that Plan Replayer might report an error when importing a table structure containing Placement Rules #54961 @hawkingrei
  • Fix the issue that when parsing a database name in CTE, it returns a wrong database name #54582 @hawkingrei
  • Fix the issue that the INSERT ... ON DUPLICATE KEY statement is not compatible with mysql_insert_id #55965 @tiancaiamao
  • Fix the issue that improper use of metadata locks might lead to writing anomalous data when using the plan cache under certain circumstances #53634 @zimulala
  • Fix the issue that the performance is unstable when adding indexes using Global Sort #54147 @tangenta
  • Fix the issue that Plan Replayer might report an error when importing a table structure containing foreign keys #56456 @hawkingrei
  • Fix the issue that using the RANGE COLUMNS partition function and the utf8mb4_0900_ai_ci collation at the same time could result in incorrect query results #57261 @Defined2014
  • Fix the issue that using subqueries after the NATURAL JOIN or USING clause might result in errors #53766 @dash12653
  • Fix the issue that TTL tasks cannot be canceled when there is a write conflict #56422 @YangKeao
  • Fix the issue that if a CTE contains the ORDER BY, LIMIT, or SELECT DISTINCT clause and is referenced by the recursive part of another CTE, it might be incorrectly inlined and result in an execution error #56603 @elsa0520
  • Fix the issue that the UPDATE statement incorrectly updates values of the ENUM type #56832 @xhebox
  • Fix the issue that executing RECOVER TABLE BY JOB JOB_ID; might cause TiDB to panic #55113 @crazycs520
  • Fix the issue that the read_from_storage hint might not take effect when the query has an available Index Merge execution plan #56217 @AilinKid
  • Fix the issue that INDEX_HASH_JOIN might hang during an abnormal exit #54055 @wshwsh12
  • Fix the issue that querying system tables related to the Distributed eXecution Framework (DXF) might lead to upgrade failures #49263 @D3Hunter
  • Fix the issue that the DDL internal transaction error GC life time is shorter than transaction duration causes index addition to fail #57043 @tangenta
  • Fix the issue that when executing EXCHANGE PARTITION and encountering invalid rows, InfoSchema is fully loaded and the error failed to load schema diff is reported #56685 @D3Hunter
  • Fix the issue that collation is not handled correctly when tidb_ddl_enable_fast_reorg and new_collations_enabled_on_first_bootstrap are enabled, resulting in inconsistent data indexes #58036 @djshow832
  • Fix the issue that data indexes are inconsistent because plan cache uses the wrong schema when adding indexes #56733 @wjhuang2016
  • Fix the issue that executing ALTER TABLE TIFLASH REPLICA during upgrade causes the TiDB node to crash #57863 @tangenta
  • Fix the issue that the performance of querying INFORMATION_SCHEMA.columns degrades #58184 @lance6716
  • Fix the issue that the default timeout for querying the TiFlash system table is too short #57816 @JaySon-Huang
  • Fix the issue that the value of the default_collation_for_utf8mb4 variable does not work for the SET NAMES statement #56439 @Defined2014
  • Fix the issue that TTL internal coroutine might panic when you manually delete a timer in the mysql.tidb_timer table #57112 @lcwangchao
  • Fix the issue that when converting a normal table to a partitioned table using the ALTER TABLE statement, insufficient checks might result in incorrect data #55721 @mjonss
  • Fix the issue that when setting tidb_gogc_tuner_max_value and tidb_gogc_tuner_min_value, if the maximum value is null, an incorrect warning message occurs #57889 @hawkingrei
  • Fix the potential data race issue that might occur in TiDB's internal coroutine #57798 #56053 @fishiu @tiancaiamao
  • Update golang-jwt and jwt to prevent potential security risks #57135 @hawkingrei
  • Fix the issue that concurrent writes might result in duplicate data when converting a table with clustered indexes to a partitioned table using the ALTER TABLE statement #57510 @mjonss

• TiKV

  • Fix the issue that merging Regions might cause TiKV to panic in rare cases #17840 @glorv
  • Fix the issue that when Raft and RocksDB are deployed on different disks, the slow disk detection does not work for the disk where RocksDB is located #17884 @LykxSassinator
  • Fix the issue that the output of jprof is not correctly captured and processed when the log-file parameter is not specified #17607 @Hexilee
  • Fix the issue that latency might increase when hibernated Regions are awake #17101 @Connor1996
  • Fix the issue that TiKV might panic when executing queries containing RADIANS() or DEGREES() functions #17852 @gengliqi
  • Fix the panic issue that occurs when read threads access outdated indexes in the MemTable of the Raft Engine #17383 @LykxSassinator
  • Fix the issue that when a large number of transactions are queuing for lock release on the same key and the key is frequently updated, excessive pressure on deadlock detection might cause TiKV OOM issues #17394 @MyonKeminta
  • Fix the issue that write jitter might occur when all hibernated Regions are awakened #17101 @hhwyt
  • Fix the issue that TiKV converts the time zone incorrectly for Brazil and Egypt #16220 @overvenus
  • Fix the issue that Online Unsafe Recovery cannot handle merge abort #15580 @v01dstar
  • Fix the issue that CPU profiling flag is not reset correctly when an error occurs #17234 @Connor1996
  • Fix the issue that large batch writes cause performance jitter when raft-entry-max-size is set too high #17701 @SpadeA-Tang
  • Fix the issue that improper error handling in the conflict detection interface of the import module might cause TiKV to panic #17830 @joccau

• PD

  • Fix the issue that when creating evict-leader-scheduler or grant-leader-scheduler encounters an error, the error message is not returned to pd-ctl #8759 @okJiang
  • Fix the issue that PD cannot quickly re-elect a leader during etcd leader transition #8823 @rleungx
  • Fix the memory leak issue in label statistics #8700 @lhy1024
  • Fix the issue that evict-leader-scheduler fails to work properly when it is repeatedly created with the same Store ID #8756 @okJiang
  • Fix the issue that slots are not fully deleted in a resource group client, which causes the number of the allocated tokens to be less than the specified value #7346 @guo-shaoge
  • Fix the issue that when using a wrong parameter in evict-leader-scheduler, PD does not report errors correctly and some schedulers are unavailable #8619 @rleungx
  • Fix the memory leak issue in hotspot cache #8698 @lhy1024
  • Fix the performance jitter issue caused by frequent creation of random number generator #8674 @rleungx

• TiFlash

  • Fix the TiFlash panic issue when TiFlash encounters conflicts during concurrent DDL execution #8578 @JaySon-Huang
  • Fix the issue that LPAD() and RPAD() functions return incorrect results in some cases #9465 @guo-shaoge
  • Fix the issue that the SUBSTRING() function returns incorrect results when the second parameter is negative #9604 @guo-shaoge
  • Fix the issue that TiFlash fails to parse the table schema when the table contains Bit-type columns with a default value that contains invalid characters #9461 @Lloyd-Pottiger
  • Fix the issue that querying new columns might return incorrect results under the disaggregated storage and compute architecture #9665 @zimulala

• Tools

  • Backup & Restore (BR)

    • Fix the issue that when resuming from a checkpoint after data restore fails, an error the target cluster is not fresh occurs #50232 @Leavrth
    • Fix the issue that log backups cannot resolve residual locks promptly, causing the checkpoint to fail to advance #57134 @3pointer
    • Fix the issue that logs might print out encrypted information #57585 @kennytm
    • Fix the issue that the TestStoreRemoved test case is unstable #52791 @YuJuncen
    • Fix potential security vulnerabilities by upgrading the k8s.io/api library version #57790 @BornChanger
    • Fix the issue that PITR tasks might return the Information schema is out of date error when there are a large number of tables in the cluster but the actual data size is small #57743 @Tristan1900

  • TiCDC

    • Fix the issue that TiCDC might report an error when replicating a TRUNCATE TABLE DDL on a table without valid index #11765 @asddongmen
    • Fix the issue that the tableID for partitioned tables is not correctly set in Simple Protocol messages #11846 @3AceShowHand
    • Fix the issue that the redo module fails to properly report errors #11744 @CharlesCheung96
    • Fix the issue that after filtering out add table partition events is configured in ignore-event, TiCDC does not replicate other types of DML changes for related partitions to the downstream #10524 @CharlesCheung96
    • Fix the issue that TiCDC mistakenly discards DDL tasks when the schema versions of DDL tasks become non-incremental during TiDB DDL owner changes #11714 @wlwilliamx

  • TiDB Data Migration (DM)

    • Fix the issue that automatically generated IDs in a table might have significant jumps after data import in physical import mode #11768 @D3Hunter
    • Fix the issue that the pre-check of start-task fails when both TLS and shard-mode are configured #11842 @sunxiaoguang
    • Fix the issue that connecting to MySQL 8.0 fails when the password length exceeds 19 characters #11603 @fishiu

  • TiDB Lightning

    • Fix the issue that TiDB Lightning fails to receive oversized messages sent from TiKV #56114 @fishiu
    • Fix the issue that the AUTO_INCREMENT value is set too high after importing data using the physical import mode #56814 @D3Hunter
    • Fix the issue that TiDB Lightning does not automatically retry when encountering Lock wait timeout errors during metadata updates #53042 @guoshouyan
    • Fix the issue that the performance degrades when importing data from a cloud storage in high-concurrency scenarios #57413 @xuanyu66
    • Fix the issue that TiDB Lightning might get stuck for a long time during the preparation phase when importing a large number of Parquet files #56104 @zeminzhou
    • Fix the issue that the error report output is truncated when importing data using TiDB Lightning #58085 @lance6716

  • Dumpling

    • Fix the issue that Dumpling fails to retry properly when receiving a 503 error from Google Cloud Storage (GCS) #56127 @OliverS929