add release notes 8.5.6

releases/release-8.5.6.md

@@ -0,0 +1,192 @@
+---
+title: TiDB 8.5.6 Release Notes
+summary: Understand the compatibility changes, improvements, and bug fixes in the TiDB 8.5.6 release.
+---
+
+# TiDB 8.5.6 Release Notes
+
+Release Date: 2026-xx-xx
+
+TiDB Version: 8.5.6
+
+Try it out: [Quick Start](https://docs.pingcap.com/tidb/v8.5/quick-start-with-tidb) | [Production Deployment](https://docs.pingcap.com/tidb/v8.5/production-deployment-using-tiup) | [Download Offline Package](https://pingkai.cn/download#tidb-community)
+
+## Feature Details
+
+### Stability
+
+- The ability to set resource limits for background tasks in Resource Control is now Generally Available (GA) [#56019](https://github.com/pingcap/tidb/issues/56019) @[glorv](https://github.com/glorv) **tw@hfxsd** <!--1933-->
+
+    TiDB Resource Control can identify and lower the priority of background tasks. In some scenarios, even with idle resources, users may want to keep the consumption of background tasks at a very low level. Starting from v8.4.0, you can use the `UTILIZATION_LIMIT` parameter to set the maximum percentage of resources that background tasks under Resource Control can use, controlling the usage of all background tasks on each node below this percentage. This feature allows you to finely control the resource consumption of background tasks, further enhancing cluster stability.
+
+    In v8.5.6, this feature is Generally Available (GA).
+
+    For more information, please refer to the [User Documentation](/tidb-resource-control-background-tasks.md).
+
+### 可观测性
+
+- 支持多维度、多粒度定义慢查询日志的触发规则（GA）[#62959](https://github.com/pingcap/tidb/issues/62959) @[zimulala](https://github.com/zimulala) **tw@lilin90** <!--2068-->
+
+	当前 TiDB 定位慢查询语句的主要方法是设置系统变量 tidb_slow_log_threshold，该机制触发慢日志控制粒度粗（整个实例级别全局控制，不支持会话和SQL级别精细化控制）、触发条件仅执行时间（Query_time）一种，无法满足复杂场景慢日志抓取以精细化定位问题的需求。
+
+	本功能通过设置 tidb_slow_log_rules 系统变量，支持用户在实例、会话、SQL级别定义多维度（如 Query_time、Digest、Mem_max、KV_total 等等）的慢查询日志抓取规则，实现更灵活的精细化控制。
+
+	在 v8.5.6 中，该功能成为正式功能（GA）。
+
+	更多信息，请参考 [用户文档](/identify-slow-queries.md)。
+
+- TOP SQL 增加网络流量和逻辑IO 数据（GA）[#62916](https://github.com/pingcap/tidb/issues/62916) @[yibin87](https://github.com/yibin87) **tw@qiancai** <!--2398-->
+
+	当前 TiDB TOP SQL 中仅包含 CPU 的相关指标数据，在遇到复杂情况时不利于排查问题。
+
+	本功能在 Top SQL 设置中增加开启 **TiKV 网络I0 采集（多维度）**，方便用户进一步查看指定 TiKV 实例的 Network Bytes、Logical IO Bytes 等指标，并按 By Query、By Table、By DB 或 By Region 维度进行聚合分析。
+
+	在 v8.5.6 中，该功能成为正式功能（GA）。
+
+    更多信息，请参考 [用户文档](/dashboard/top-sql.md)。
+
+### Data Migration
+
+- (dup): release-9.0.0.md > # Data migration * Migrate sync-diff-inspector from `pingcap/tidb-tools` to `pingcap/tiflow` repository [#11672](https://github.com/pingcap/tiflow/issues/11672) @[joechenrh](https://github.com/joechenrh)
+
+## Compatibility Changes
+
+- note [#issue](https://github.com/pingcap/${repo-name}/issues/${issue-id}) @[Contributor GitHub ID](https://github.com/${github-id})
+
+## Improvements
+
++ TiDB
+
+    - Enhanced slow query log control by supporting [`tidb_slow_log_rules`](/system-variables.md#tidb_slow_log_rules-new-in-v900) for targeted slow query log output based on combinations of multiple metrics, [`tidb_slow_log_max_per_sec`](/system-variables.md#tidb_slow_log_max_per_sec-new-in-v900) for limiting the number of slow query log entries per second, and the [`WRITE_SLOW_LOG`](/identify-slow-queries.md#related-hint) hint for forcing specified SQL statements to be recorded in the slow query log [#64010](https://github.com/pingcap/tidb/issues/64010) @[zimulala](https://github.com/zimulala)
+    - Enhanced [Top SQL](/dashboard/top-sql.md) for resource analysis by supporting Top `5`, `20`, or `100` queries, hotspot analysis sorted by CPU, network traffic, or logical I/O, and aggregated analysis by `Query`, `Table`, `DB`, or `Region` on TiKV instances [#62916](https://github.com/pingcap/tidb/issues/62916) @[yibin87](https://github.com/yibin87)
+    - 新增 DXF 的 max_node_count 配置项支持 [#66376](https://github.com/pingcap/tidb/pull/66376)@[D3Hunter](https://github.com/D3Hunter)
+    - 调整部分 stats 相关日志为 warning 级别 [#58315](https://github.com/pingcap/tidb/pull/58315)@[hawkingrei](https://github.com/hawkingrei)
+    - 调整 tidb_analyze_column_options 默认值为 all [#64992](https://github.com/pingcap/tidb/issues/64992) @[0xPoe](https://github.com/0xPoe)
+
++ TiKV
+
+    - Add MVCC-read-aware load-based compaction to prioritize regions with heavy MVCC read overhead. [#19133](https://github.com/tikv/tikv/issues/19133) @[mittalrishabh](https://github.com/mittalrishabh)
+    - Optimize stale-range cleanup during scaling by deleting stale keys directly instead of ingesting SST files, reducing latency impact. [#18042](https://github.com/tikv/tikv/issues/18042) @[LykxSassinator](https://github.com/LykxSassinator)
+    - Make default gRPC raft connection and concurrency settings scale with CPU quota to improve resource utilization. [#18613](https://github.com/tikv/tikv/issues/18613) @[LykxSassinator](https://github.com/LykxSassinator)
+    - Add Top SQL support for collecting network traffic and logical I/O information to help diagnose SQL performance issues. [#18815](https://github.com/tikv/tikv/issues/18815) @[yibin87](https://github.com/yibin87)
+
++ PD
+
+    - note [#issue](https://github.com/tikv/pd/issues/${issue-id}) @[Contributor GitHub ID](https://github.com/${github-id})
+    - note [#issue](https://github.com/tikv/pd/issues/${issue-id}) @[Contributor GitHub ID](https://github.com/${github-id})
+    - (dup): release-7.5.7.md > Improvements> PD - Reduce unnecessary error logs [#9370](https://github.com/tikv/pd/issues/9370) @[bufferflies](https://github.com/bufferflies)
+
++ TiFlash
+
+    - note [#issue](https://github.com/pingcap/tiflash/issues/${issue-id}) @[Contributor GitHub ID](https://github.com/${github-id})
+    - note [#issue](https://github.com/pingcap/tiflash/issues/${issue-id}) @[Contributor GitHub ID](https://github.com/${github-id})
+
++ Tools
+
+    + Backup & Restore (BR)
+
+        - note [#issue](https://github.com/pingcap/tidb/issues/${issue-id}) @[Contributor GitHub ID](https://github.com/${github-id})
+        - note [#issue](https://github.com/pingcap/tidb/issues/${issue-id}) @[Contributor GitHub ID](https://github.com/${github-id})
+
+    + TiCDC
+
+        - note [#issue](https://github.com/pingcap/tiflow/issues/${issue-id}) @[Contributor GitHub ID](https://github.com/${github-id})
+        - note [#issue](https://github.com/pingcap/tiflow/issues/${issue-id}) @[Contributor GitHub ID](https://github.com/${github-id})
+
+    + TiDB Data Migration (DM)
+
+        - note [#issue](https://github.com/pingcap/tiflow/issues/${issue-id}) @[Contributor GitHub ID](https://github.com/${github-id})
+        - note [#issue](https://github.com/pingcap/tiflow/issues/${issue-id}) @[Contributor GitHub ID](https://github.com/${github-id})
+        - Support migrating data from MySQL 8.4 as a data source. The compatibility level for MySQL 8.4 is upgraded from "Incompatible" to "Experimental" [#11020](https://github.com/pingcap/tiflow/issues/11020) @[dveeden](https://github.com/dveeden)
+
+    + TiDB Lightning
+
+        - note [#issue](https://github.com/pingcap/tidb/issues/${issue-id}) @[Contributor GitHub ID](https://github.com/${github-id})
+        - note [#issue](https://github.com/pingcap/tidb/issues/${issue-id}) @[Contributor GitHub ID](https://github.com/${github-id})
+
+    + Dumpling
+
+        - note [#issue](https://github.com/pingcap/tidb/issues/${issue-id}) @[Contributor GitHub ID](https://github.com/${github-id})
+        - note [#issue](https://github.com/pingcap/tidb/issues/${issue-id}) @[Contributor GitHub ID](https://github.com/${github-id})
+        - Support exporting data from MySQL 8.4 by adopting the updated MySQL binary log terminology [#53082](https://github.com/pingcap/tidb/issues/53082) @[dveeden](https://github.com/dveeden)
+
+    + TiUP
+
+        - note [#issue](https://github.com/pingcap/tiup/issues/${issue-id}) @[Contributor GitHub ID](https://github.com/${github-id})
+        - note [#issue](https://github.com/pingcap/tiup/issues/${issue-id}) @[Contributor GitHub ID](https://github.com/${github-id})
+
+## Bug Fixes
+
++ TiDB
+
+    - Fix the issue that upgrading from release-8.5-20250606-v8.5.2 to upstream release-8.5 can skip PITR metadata upgrades and cause PITR operations to fail. [#66994](https://github.com/pingcap/tidb/issues/66994) @[fzzf678](https://github.com/fzzf678)
+    - Fix the issue that after EXCHANGE PARTITION, non-unique or nullable unique global indexes on non-clustered partitioned tables can become inconsistent and return incomplete results. [#65289](https://github.com/pingcap/tidb/issues/65289) @[mjonss](https://github.com/mjonss)
+    - Support column-level privileges in GRANT and REVOKE. [#61706](https://github.com/pingcap/tidb/issues/61706) @[CbcWestwolf](https://github.com/CbcWestwolf)
+    - Improve the performance of privilege updates such as GRANT and REVOKE in deployments with large numbers of privilege entries. [#61706](https://github.com/pingcap/tidb/issues/61706) @[CbcWestwolf](https://github.com/CbcWestwolf)
+    - Fix the issue that KILL QUERY incorrectly kills idle connections. [#65447](https://github.com/pingcap/tidb/issues/65447) @[gengliqi](https://github.com/gengliqi)
+    - Fix the issue that column-level privilege checks can be incorrect for JOIN ... USING, NATURAL JOIN, and INSERT ... ON DUPLICATE KEY UPDATE. [#61706](https://github.com/pingcap/tidb/issues/61706) @[CbcWestwolf](https://github.com/CbcWestwolf)
+    - Improve privilege-check performance for deployments with many column-level privilege entries. [#61706](https://github.com/pingcap/tidb/issues/61706) @[CbcWestwolf](https://github.com/CbcWestwolf)
+    - Add cluster_id to mysql.tidb so external tools can determine whether two TiDB instances belong to the same cluster. [#59476](https://github.com/pingcap/tidb/issues/59476) @[YangKeao](https://github.com/YangKeao)
+    - Improve the slow query log by printing non-printable prepared-statement arguments as hexadecimal literals. [#65383](https://github.com/pingcap/tidb/issues/65383) @[dveeden](https://github.com/dveeden)
+    - 修复 tidb_service_scope 设置时未统一转换为小写的问题 [#66835](https://github.com/pingcap/tidb/pull/66835)@[D3Hunter](https://github.com/D3Hunter)
+    - 修复 TiDB 重启后无法展示亲和力表的问题 [#66284](https://github.com/pingcap/tidb/issues/66284) @[lcwangchao](https://github.com/lcwangchao)
+    - 修复可能出现的内存泄漏 [#65522](https://github.com/pingcap/tidb/issues/65522) @[bufferflies](https://github.com/bufferflies)
+    - 修复系统表可能影响 stats healthy 监控的问题 [#64080](https://github.com/pingcap/tidb/issues/64080) @[ti-chi-bot](https://github.com/ti-chi-bot)
+    - 修复 stats delta 数据可能刷新不及时的问题 [#65426](https://github.com/pingcap/tidb/issues/65426) @[ti-chi-bot](https://github.com/ti-chi-bot)
+
++ TiKV
+
+    - Fix the issue that global indexes on non-unique columns of partitioned tables might become inconsistent and return incorrect results in some cases. [#19262](https://github.com/tikv/tikv/issues/19262) @[mjonss](https://github.com/mjonss)
+    - Fix the issue that stalled coprocessor snapshot retrieval could occupy unified read pool workers until request deadlines expired, delaying other read requests. [#18491](https://github.com/tikv/tikv/issues/18491) @[AndreMouche](https://github.com/AndreMouche)
+    - Fix the issue that follower replica reads could remain blocked on disk-full TiKV nodes by rejecting read-index requests on disk-full followers. [#19201](https://github.com/tikv/tikv/issues/19201) @[glorv](https://github.com/glorv)
+    - Fix the issue that resolved-ts task backlogs could cause OOM when the resolved-ts worker is busy. [#18359](https://github.com/tikv/tikv/issues/18359) @[overvenus](https://github.com/overvenus)
+    - Fix long-tail follower-read latency during leader transfer by retrying read-index requests sooner and adding a dedicated retry interval setting. [#18417](https://github.com/tikv/tikv/issues/18417) @[gengliqi](https://github.com/gengliqi)
+    - Fix ingest latency spikes in large clusters by increasing the default `rocksdb.max-manifest-file-size` from 128 MiB to 256 MiB. [#18996](https://github.com/tikv/tikv/issues/18996) @[glorv](https://github.com/glorv)
+    - (dup): release-5.1.4.md > Bug fixes> TiKV - Fix the rare data inconsistency issue when retrying a prewrite request in pessimistic transactions [#11187](https://github.com/tikv/tikv/issues/11187)
+
++ PD
+
+    - note [#issue](https://github.com/tikv/pd/issues/${issue-id}) @[Contributor GitHub ID](https://github.com/${github-id})
+    - note [#issue](https://github.com/tikv/pd/issues/${issue-id}) @[Contributor GitHub ID](https://github.com/${github-id})
+
++ TiFlash
+
+    - 修复当一个列执行将列属性 `NOT NULL` 转为 `NULL` 的 DDL 之后，TiFlash 与 TiKV 之间可能产生不一致数据的问题 [#10680](https://github.com/pingcap/tiflash/issues/10680) @[JaySon-Huang](https://github.com/JaySon-Huang)
+    - 修复 Grafana 面板中 Raft throughput 可能会错误地显示一个非常大的数值的问题 [#10701](https://github.com/pingcap/tiflash/issues/10701) @[CalvinNeo](https://github.com/CalvinNeo)
+    - 修复 runtime filter 开启情况下，如果 join key 数据类型不一致时，join 结果可能出错的问题 [#10699](https://github.com/pingcap/tiflash/issues/10699) @[ChangRui-Ryan](https://github.com/ChangRui-Ryan)
+
++ Tools
+
+    + Backup & Restore (BR)
+
+        - 修复了 log backup 的 flush_ts 可能为 0 的问题 [#19406](https://github.com/tikv/tikv/issues/19406) @[YuJuncen](https://github.com/YuJuncen)
+        - 修复 BR 在使用 GCP S3 API server 进行 multipart upload 时因缺少 `Content-Length` 头而失败的问题 [#19352](https://github.com/tikv/tikv/issues/19352) @[Leavrth](https://github.com/Leavrth)
+        - 修复 BR `restore point` 可能长时间卡在 `waiting for schema info finishes reloading` 并在 15 分钟后超时失败的问题 [#66110](https://github.com/pingcap/tidb/issues/66110) @[kennytm](https://github.com/kennytm)
+        - 修复 BR 在恢复带有 `SHARD_ROW_ID_BITS`、`PRE_SPLIT_REGIONS` 和 `merge_option` 属性的表时无法正确预分裂 Region 的问题 [#65060](https://github.com/pingcap/tidb/issues/65060) @[JoyC-dev](https://github.com/JoyC-dev)
+
+    + TiCDC
+
+        - Fixed an issue where changefeed might repeatedly create invalid dispatchers when the server restarts. [#4452](https://github.com/pingcap/ticdc/issues/4452) @[wlwilliamx](https://github.com/wlwilliamx)
+        - Fixed an issue where table renaming operations could not be performed normally when the upstream TiDB version was <= v8.1.x. [#4392](https://github.com/pingcap/ticdc/issues/4392) @[lidezhu](https://github.com/lidezhu)
+        - Fixed a bug during data scanning to avoid potential abnormal crashes of TiKV when CDC is enabled. [#19404](https://github.com/tikv/tikv/issues/19404) @[wk989898](https://github.com/wk989898)
+        - Supported Azure Managed Identity authentication for azblob sinks and fixed a potential stuck issue during cloud storage uploads. [#3093](https://github.com/pingcap/ticdc/issues/3093) @[wlwilliamx](https://github.com/wlwilliamx)
+
+    + TiDB Data Migration (DM)
+
+        - note [#issue](https://github.com/pingcap/tiflow/issues/${issue-id}) @[Contributor GitHub ID](https://github.com/${github-id})
+        - note [#issue](https://github.com/pingcap/tiflow/issues/${issue-id}) @[Contributor GitHub ID](https://github.com/${github-id})
+
+    + TiDB Lightning
+
+        - note [#issue](https://github.com/pingcap/tidb/issues/${issue-id}) @[Contributor GitHub ID](https://github.com/${github-id})
+        - note [#issue](https://github.com/pingcap/tidb/issues/${issue-id}) @[Contributor GitHub ID](https://github.com/${github-id})
+
+    + Dumpling
+
+        - note [#issue](https://github.com/pingcap/tidb/issues/${issue-id}) @[Contributor GitHub ID](https://github.com/${github-id})
+        - note [#issue](https://github.com/pingcap/tidb/issues/${issue-id}) @[Contributor GitHub ID](https://github.com/${github-id})
+
+    + TiUP
+
+        - note [#issue](https://github.com/pingcap/tiup/issues/${issue-id}) @[Contributor GitHub ID](https://github.com/${github-id})
+        - note [#issue](https://github.com/pingcap/tiup/issues/${issue-id}) @[Contributor GitHub ID](https://github.com/${github-id})