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Update the Compatibility changes of release-8.5.4 #21215

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46 changes: 26 additions & 20 deletions releases/release-8.5.4.md
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Expand Up @@ -61,26 +61,32 @@ TiDB 版本：8.5.4

## 兼容性变更

### 系统变量

- 系统变量 [`tidb_mpp_store_fail_ttl`](https://docs.pingcap.com/zh/tidb/v8.5/system-variables/#tidb_mpp_store_fail_ttl) 默认值从 `60s` 修改为 `0s`，意味着 TiDB 不再需要额外等待即可向新启动的 TiFlash 节点发送查询请求，无需再通过延迟来避免查询失败 [#61826](https://github.com/pingcap/tidb/issues/61826) @[gengliqi](https://github.com/gengliqi)

- 系统变量 [`tidb_replica_read`](https://docs.pingcap.com/zh/tidb/v8.5/system-variables/#tidb_replica_read-从-v40-版本开始引入) 从 v8.5.4 开始仅对只读 SQL 语句生效，以提高数据读取的安全性并减少与其他功能的重叠 [#62856](https://github.com/pingcap/tidb/issues/62856) @[you06](https://github.com/you06)

- 新增以下系统变量：

- [`tidb_opt_enable_no_decorrelate_in_select`](https://docs.pingcap.com/zh/tidb/v8.5/system-variables/#tidb_opt_enable_no_decorrelate_in_select-从-v854-版本开始引入)：控制是否对 `SELECT` 列表中的子查询进行解关联操作，默认值为 `OFF` [#51116](https://github.com/pingcap/tidb/issues/51116) @[terry1purcell](https://github.com/terry1purcell)
- [`tidb_opt_enable_semi_join_rewrite`](https://docs.pingcap.com/zh/tidb/v8.5/system-variables/#tidb_opt_enable_semi_join_rewrite-从-v854-版本开始引入)：控制是否改写 `EXISTS` 子查询，默认值为 `OFF` [#44850](https://github.com/pingcap/tidb/issues/44850) @[terry1purcell](https://github.com/terry1purcell)
- [`tidb_stats_update_during_ddl`](https://docs.pingcap.com/zh/tidb/v8.5/system-variables/#tidb_stats_update_during_ddl-从-v854-版本开始引入)：控制是否开启内嵌于 DDL 的 Analyze 特性，默认值为 `OFF` [#57948](https://github.com/pingcap/tidb/issues/57948) @[terry1purcell](https://github.com/terry1purcell) @[AilinKid](https://github.com/AilinKid)

### 配置参数

- 废弃以下 TiKV 配置项，并由新的 [`gc.auto-compaction`](https://docs.pingcap.com/zh/tidb/v8.5/tikv-configuration-file/#gcauto-compaction) 配置项替代，用于控制自动 compaction 行为 [#18727](https://github.com/tikv/tikv/issues/18727) @[v01dstar](https://github.com/v01dstar)

- 废弃配置项：[`region-compact-check-interval`](https://docs.pingcap.com/zh/tidb/v8.5/tikv-configuration-file#region-compact-check-interval)、[`region-compact-check-step`](https://docs.pingcap.com/zh/tidb/v8.5/tikv-configuration-file#region-compact-check-step)、[`region-compact-min-tombstones`](https://docs.pingcap.com/zh/tidb/v8.5/tikv-configuration-file#region-compact-min-tombstones)、[`region-compact-tombstones-percent`](https://docs.pingcap.com/zh/tidb/v8.5/tikv-configuration-file#region-compact-tombstones-percent)、[`region-compact-min-redundant-rows`](https://docs.pingcap.com/zh/tidb/v8.5/tikv-configuration-file#region-compact-min-redundant-rows-从-v710-版本开始引入) 和 [`region-compact-redundant-rows-percent`](https://docs.pingcap.com/zh/tidb/v8.5/tikv-configuration-file#region-compact-redundant-rows-percent-从-v710-版本开始引入)。
- 新增配置项：[`gc.auto-compaction.check-interval`](https://docs.pingcap.com/zh/tidb/v8.5/tikv-configuration-file#check-interval-从-v757-和-v854-版本开始引入)、[`gc.auto-compaction.tombstone-num-threshold`](https://docs.pingcap.com/zh/tidb/v8.5/tikv-configuration-file#tombstone-num-threshold-从-v757-和-v854-版本开始引入)、[`gc.auto-compaction.tombstone-percent-threshold`](https://docs.pingcap.com/zh/tidb/v8.5/tikv-configuration-file#tombstone-percent-threshold-从-v757-和-v854-版本开始引入)、[`gc.auto-compaction.redundant-rows-threshold`](https://docs.pingcap.com/zh/tidb/v8.5/tikv-configuration-file#redundant-rows-threshold-从-v757-和-v854-版本开始引入)、[`gc.auto-compaction.redundant-rows-percent-threshold`](https://docs.pingcap.com/zh/tidb/v8.5/tikv-configuration-file#redundant-rows-percent-threshold-从-v757-和-v854-版本开始引入) 和 [`gc.auto-compaction.bottommost-level-force`](https://docs.pingcap.com/zh/tidb/v8.5/tikv-configuration-file#bottommost-level-force-从-v757-和-v854-版本开始引入)。

- 新增 TiFlash 配置项 [`flash.graceful_wait_shutdown_timeout`](https://docs.pingcap.com/zh/tidb/v8.5/tiflash-configuration#graceful_wait_shutdown_timeout-从-v854-版本开始引入)，用于控制在关闭 TiFlash 服务器时的最长等待时间，默认值为 `600` 秒。在此期间，TiFlash 允许尚未完成的 MPP 任务继续执行，但不再接收新的 MPP 任务。如果所有正在运行的 MPP 任务都在此超时时间之前完成，TiFlash 将立即关闭；否则将在等待时间结束后强制关闭。 [#10266](https://github.com/pingcap/tiflash/issues/10266) @[gengliqi](https://github.com/gengliqi)
## 要点

- 新建的 v8.5.3 集群可以平滑升级到 v8.5.4。但本次发布包含若干系统变量和配置参数的默认值变更和行为调整，需要注意。
- 大多数变更对于常规升级是安全的，但对于进行过性能调优、使用 TiFlash 或 TiKV compaction 自定义配置的集群，需要仔细检查本节内容。
- 一些老旧配置项已被废弃，不再推荐使用，建议使用新的配置组。

## 系统变量

| 变量 | 类型 | 默认值 | 描述 | PR | 提交者 |
|------|------|--------|------|----|-------------|
| [`tidb_mpp_store_fail_ttl`](https://docs.pingcap.com/zh/tidb/v8.5/system-variables/#tidb_mpp_store_fail_ttl) | 默认值变更 | `0` | 默认值从 `60s` → `0s`。TiDB 不再需要额外等待即可向新启动的 TiFlash 节点发送查询请求，无需通过设置等待时间来避免查询失败。 | [#61826](https://github.com/pingcap/tidb/issues/61826) | [@gengliqi](https://github.com/gengliqi) |
| [`tidb_replica_read`](https://docs.pingcap.com/zh/tidb/v8.5/system-variables/#tidb_replica_read-从-v40-版本开始引入) | 行为变更 | `leader` | 从 v8.5.4 开始，仅对只读 SQL 语句生效，提高数据读取安全性并减少与其他功能的重叠。 | [#62856](https://github.com/pingcap/tidb/issues/62856) | [@you06](https://github.com/you06) |
| [`tidb_opt_enable_no_decorrelate_in_select`](https://docs.pingcap.com/zh/tidb/v8.5/system-variables/#tidb_opt_enable_no_decorrelate_in_select-从-v854-版本开始引入) | 新增 | `OFF` | 控制是否对 `SELECT` 列表中的子查询进行解关联操作。 | [#51116](https://github.com/pingcap/tidb/issues/51116) | [@terry1purcell](https://github.com/terry1purcell) |
| [`tidb_opt_enable_semi_join_rewrite`](https://docs.pingcap.com/zh/tidb/v8.5/system-variables/#tidb_opt_enable_semi_join_rewrite-从-v854-版本开始引入) | 新增 | `OFF` | 控制是否改写 `EXISTS` 子查询。 | [#44850](https://github.com/pingcap/tidb/issues/44850) | [@terry1purcell](https://github.com/terry1purcell) |
| [`tidb_stats_update_during_ddl`](https://docs.pingcap.com/zh/tidb/v8.5/system-variables/#tidb_stats_update_during_ddl-从-v854-版本开始引入) | 新增 | `OFF` | 启用后，`ADD INDEX` 会在 DDL 执行期间收集新索引的统计信息，使索引添加完成后，优化器可以立即使用该索引。对于大表加索引的场景可能增加 DDL 执行时间。 | [#57948](https://github.com/pingcap/tidb/issues/57948) | [@terry1purcell](https://github.com/terry1purcell), [@AilinKid](https://github.com/AilinKid) |

## 配置参数

| 配置参数 | 类型 | 默认值 | 描述 | PR | 提交者 |
|-------------------------|------|---------------|-------------|----|-------------|
| [`max-manifest-file-size`](https://docs.pingcap.com/zh/tidb/v8.5/tikv-configuration-file#max-manifest-file-size) | 默认值变更 | `256 MiB` | 将 `rocksdb.max-manifest-file-size` 默认值从 `128 MiB` 提升到 `256 MiB`，可能影响依赖之前默认值的用户。 | [#18889](https://github.com/tikv/tikv/issues/18889) | [@glorv](https://github.com/glorv) |
| [`grpc-raft-conn-num`](https://docs.pingcap.com/zh/tidb/v8.5/tikv-configuration-file#grpc-raft-conn-num) | 默认值变更 | CPU 核数 / 8 | 默认值更新为 `MAX(1, MIN(4, CPU 核数 / 8))`。当 CPU 核数 ≥ 32 时，最大默认连接数限制为 4。 | [#18806](https://github.com/tikv/tikv/issues/18806) | [@LykxSassinator](https://github.com/LykxSassinator) |
| [`grpc-concurrency`](https://docs.pingcap.com/zh/tidb/v8.5/tikv-configuration-file#grpc-concurrency) | 默认值变更 | `grpc-raft-conn-num * 3 + 2` | 默认值计算方式为 `grpc_raft_conn_num * 3 + 2`。 | [#18806](https://github.com/tikv/tikv/issues/18806) | [@LykxSassinator](https://github.com/LykxSassinator) |
| [`region-compact-check-interval`](https://docs.pingcap.com/zh/tidb/v8.5/tikv-configuration-file#region-compact-check-interval), [`region-compact-check-step`](https://docs.pingcap.com/zh/tidb/v8.5/tikv-configuration-file#region-compact-check-step), [`region-compact-min-tombstones`](https://docs.pingcap.com/zh/tidb/v8.5/tikv-configuration-file#region-compact-min-tombstones), [`region-compact-tombstones-percent`](https://docs.pingcap.com/zh/tidb/v8.5/tikv-configuration-file#region-compact-tombstones-percent), [`region-compact-min-redundant-rows`](https://docs.pingcap.com/zh/tidb/v8.5/tikv-configuration-file#region-compact-min-redundant-rows-从-v710-版本开始引入), [`region-compact-redundant-rows-percent`](https://docs.pingcap.com/zh/tidb/v8.5/tikv-configuration-file#region-compact-redundant-rows-percent-从-v710-版本开始引入) | 废弃 | – | 废弃，并由 [`gc.auto-compaction`](https://docs.pingcap.com/zh/tidb/v8.5/tikv-configuration-file/#gcauto-compaction) 配置组替代，用于控制自动 compaction 行为。 | [#18727](https://github.com/tikv/tikv/issues/18727) | [@v01dstar](https://github.com/v01dstar) |
| [`gc.auto-compaction.check-interval`](https://docs.pingcap.com/zh/tidb/stable/tikv-configuration-file/#check-interval-从-v757-版本开始引入), [`gc.auto-compaction.tombstone-num-threshold`](https://docs.pingcap.com/zh/tidb/stable/tikv-configuration-file/#tombstone-num-threshold-从-v757-版本开始引入), [`gc.auto-compaction.tombstone-percent-threshold`](https://docs.pingcap.com/zh/tidb/v8.5/tikv-configuration-file#tombstone-percent-threshold-从-v757-版本开始引入), [`gc.auto-compaction.redundant-rows-threshold`](https://docs.pingcap.com/zh/tidb/v8.5/tikv-configuration-file#redundant-rows-threshold-从-v757-版本开始引入), [`gc.auto-compaction.redundant-rows-percent-threshold`](https://docs.pingcap.com/zh/tidb/v8.5/tikv-configuration-file#redundant-rows-percent-threshold-从-v757-版本开始引入), [`gc.auto-compaction.bottommost-level-force`](https://docs.pingcap.com/zh/tidb/v8.5/tikv-configuration-file#bottommost-level-force-从-v757-版本开始引入) | 新增 | – | 新增配置组，用于控制自动 compaction 行为。 | [#18727](https://github.com/tikv/tikv/issues/18727) | [@v01dstar](https://github.com/v01dstar) |
| [`flash.graceful_wait_shutdown_timeout`](https://docs.pingcap.com/zh/tidb/v8.5/tiflash-configuration#graceful_wait_shutdown_timeout-从-v854-版本开始引入) | 新增 | `600` | TiFlash 优雅关闭最长等待时间（秒）。TiFlash 会继续执行未完成的 MPP 任务，但不再接收新的任务。如果所有任务在超时时间前完成，TiFlash 将立即关闭；否则等待时间结束后强制关闭。 | [#10266](https://github.com/pingcap/tiflash/issues/10266) | [@gengliqi](https://github.com/gengliqi) |

### MySQL 兼容性

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