add release notes 8.5.6

releases/release-8.5.6.md

@@ -0,0 +1,151 @@
+---
+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).
+
+### 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/${github-id})
+
+## Improvements
+
++ TiDB
+
+    - Enhanced slow query log control by supporting [`tidb_slow_log_rules`](/system-variables.md#tidb_slow_log_rules-new-in-v900) for targeted slow query log output based on combinations of multiple metrics, [`tidb_slow_log_max_per_sec`](/system-variables.md#tidb_slow_log_max_per_sec-new-in-v900) for limiting the number of slow query log entries per second, and the [`WRITE_SLOW_LOG`](/identify-slow-queries.md#related-hint) hint for forcing specified SQL statements to be recorded in the slow query log [#64010](https://github.com/pingcap/tidb/issues/64010) @[zimulala](https://github.com/zimulala)
+    - Enhanced [Top SQL](/dashboard/top-sql.md) for resource analysis by supporting Top `5`, `20`, or `100` queries, hotspot analysis sorted by CPU, network traffic, or logical I/O, and aggregated analysis by `Query`, `Table`, `DB`, or `Region` on TiKV instances [#62916](https://github.com/pingcap/tidb/issues/62916) @[yibin87](https://github.com/yibin87)
+    - note [#issue](https://github.com/pingcap/tidb/issues/${issue-id}) @[Contributor GitHub ID](https://github.com/${github-id})
+
++ TiKV
+
+    - Add MVCC-read-aware load-based compaction to prioritize regions with heavy MVCC read overhead. [#19133](https://github.com/tikv/tikv/issues/19133) @[mittalrishabh](https://github.com/mittalrishabh)
+    - Optimize stale-range cleanup during scaling by deleting stale keys directly instead of ingesting SST files, reducing latency impact. [#18042](https://github.com/tikv/tikv/issues/18042) @[LykxSassinator](https://github.com/LykxSassinator)
+    - Make default gRPC raft connection and concurrency settings scale with CPU quota to improve resource utilization. [#18613](https://github.com/tikv/tikv/issues/18613) @[LykxSassinator](https://github.com/LykxSassinator)
+    - Add Top SQL support for collecting network traffic and logical I/O information to help diagnose SQL performance issues. [#18815](https://github.com/tikv/tikv/issues/18815) @[yibin87](https://github.com/yibin87)
+
++ PD
+
+    - note [#issue](https://github.com/tikv/pd/issues/${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/${github-id})
+
+    + TiDB Lightning
+
+        - note [#issue](https://github.com/pingcap/tidb/issues/${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/${github-id})
+
+## Bug Fixes
+
++ TiDB
+
+    - note [#issue](https://github.com/pingcap/tidb/issues/${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/${github-id})
+
++ TiKV
+
+    - Fix the issue that global indexes on non-unique columns of partitioned tables might become inconsistent and return incorrect results in some cases. [#19262](https://github.com/tikv/tikv/issues/19262) @[mjonss](https://github.com/mjonss)
+    - Fix the issue that stalled coprocessor snapshot retrieval could occupy unified read pool workers until request deadlines expired, delaying other read requests. [#18491](https://github.com/tikv/tikv/issues/18491) @[AndreMouche](https://github.com/AndreMouche)
+    - Fix the issue that follower replica reads could remain blocked on disk-full TiKV nodes by rejecting read-index requests on disk-full followers. [#19201](https://github.com/tikv/tikv/issues/19201) @[glorv](https://github.com/glorv)
+    - Fix the issue that resolved-ts task backlogs could cause OOM when the resolved-ts worker is busy. [#18359](https://github.com/tikv/tikv/issues/18359) @[overvenus](https://github.com/overvenus)
+    - Fix long-tail follower-read latency during leader transfer by retrying read-index requests sooner and adding a dedicated retry interval setting. [#18417](https://github.com/tikv/tikv/issues/18417) @[gengliqi](https://github.com/gengliqi)
+    - Fix ingest latency spikes in large clusters by increasing the default `rocksdb.max-manifest-file-size` from 128 MiB to 256 MiB. [#18996](https://github.com/tikv/tikv/issues/18996) @[glorv](https://github.com/glorv)
+    - (dup): release-5.1.4.md > Bug fixes> TiKV - Fix the rare data inconsistency issue when retrying a prewrite request in pessimistic transactions [#11187](https://github.com/tikv/tikv/issues/11187)
+
++ PD
+
+    - note [#issue](https://github.com/tikv/pd/issues/${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/${github-id})
+
++ TiFlash
+
+    - note [#issue](https://github.com/pingcap/tiflash/issues/${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/${github-id})
+
+    + TiCDC
+
+        - Fixed an issue where changefeed might repeatedly create invalid dispatchers when the server restarts. [#4452](https://github.com/pingcap/ticdc/issues/4452) @[wlwilliamx](https://github.com/wlwilliamx)
+        - Fixed an issue where table renaming operations could not be performed normally when the upstream TiDB version was <= v8.1.x. [#4392](https://github.com/pingcap/ticdc/issues/4392) @[lidezhu](https://github.com/lidezhu)
+        - Fixed a bug during data scanning to avoid potential abnormal crashes of TiKV when CDC is enabled. [#19404](https://github.com/tikv/tikv/issues/19404) @[wk989898](https://github.com/wk989898)
+        - Supported Azure Managed Identity authentication for azblob sinks and fixed a potential stuck issue during cloud storage uploads. [#3093](https://github.com/pingcap/ticdc/issues/3093) @[wlwilliamx](https://github.com/wlwilliamx)
+
+    + TiDB Data Migration (DM)
+
+        - note [#issue](https://github.com/pingcap/tiflow/issues/${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})