release-6.5.5.md

title	summary
TiDB 6.5.5 Release Notes	Learn about the improvements and bug fixes in TiDB 6.5.5.

TiDB 6.5.5 Release Notes

Release date: September 21, 2023

TiDB version: 6.5.5

Quick access: Quick start | Production deployment

Improvements

• TiDB

  • Add new optimizer hints, including NO_MERGE_JOIN(), NO_INDEX_JOIN(), NO_INDEX_MERGE_JOIN(), NO_HASH_JOIN(), and NO_INDEX_HASH_JOIN() #45520 @qw4990
  • Add request source information related to the coprocessor #46514 @you06

• TiKV

  • Add the backoff mechanism for the PD client in the process of connection retries, which gradually increases retry intervals during error retries to reduce PD pressure #15428 @nolouch
  • Add monitoring metrics for snapshots #15401 @SpadeA-Tang
  • Improve stability of PITR checkpoint lag during leader transfers #13638 @YuJuncen
  • Add logs and monitoring metrics related to safe-ts #15082 @ekexium
  • Provide more logs and monitoring metrics for resolved-ts #15082 @ekexium

• Tools

  • Backup & Restore (BR)

    • Reduce the CPU overhead of log backup resolve lock #40759 @3pointer

Bug fixes

• TiDB

  • Fix the issue that Stale Read might select an unavailable replica #46198 @zyguan
  • Fix the issue that additional overhead is incurred due to the incompatibility between Stale Read and Schema Cache #43481 @crazycs520

• TiKV

  • Fix the issue that TiKV fails to start when Titan is enabled and the Blob file deleted twice error occurs #15454 @Connor1996
  • Fix the issue that Online Unsafe Recovery cannot handle merge abort #15580 @v01dstar

• PD

  • Fix the issue that the scheduler takes a long time to start up #6920 @HuSharp
  • Fix the issue that the logic for handling Leaders and Peers in Scatter Region is inconsistent #6962 @bufferflies
  • Fix the issue that the empty-region-count monitoring metric is abnormal when the cluster is restarted or the PD Leader is switched #7008 @CabinfeverB

• Tools

  • Backup & Restore (BR)

    • Fix the issue that restoring implicit primary keys by PITR might lead to conflicts #46520 @3pointer
    • Fix the issue that an error occurs when PITR recovers the meta-kv #46578 @Leavrth
    • Fix an error in BR integration test cases #46561 @purelind
    • Fix the issue that PITR fails to restore data from GCS #47022 @Leavrth

  • TiCDC

    • Fix the issue of high TiCDC replication latency caused by network isolation of PD nodes #9565 @asddongmen
    • Fix the issue that TiCDC incorrectly changes the UPDATE operation to INSERT when using the CSV format #9658 @3AceShowHand
    • Fix the issue that user passwords are recorded in some logs #9690 @sdojjy
    • Fix the issue that using the SASL authentication might cause TiCDC to panic #9669 @sdojjy
    • Fix the issue that TiCDC replication tasks might fail in some corner cases #9685 #9697 #9695 #9736 @hicqu @CharlesCheung96
    • Fix the issue that TiCDC cannot recover quickly from TiKV node failures when there are a lot of Regions upstream #9741 @sdojjy

  • TiDB Lightning

    • Fix the issue that TiDB Lightning fails to start when TiCDC is deployed on the target server #41040 @lance6716
    • Fix the issue that TiDB Lightning fails to start when PD topology is changed #46688 @lance6716
    • Fix the issue that TiDB Lightning cannot continue importing data after PD switching Leaders #46540 @lance6716
    • Fix the issue that precheck cannot accurately detect the presence of a running TiCDC in the target cluster #41040 @lance6716