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Nov 7, 2025
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planner: Add subquery variables #21032

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planner: Add subquery variables
Oreoxmt Oct 30, 2025
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Oreoxmt Nov 4, 2025
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18 changes: 18 additions & 0 deletions system-variables.md
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Expand Up @@ -3737,6 +3737,24 @@ mysql> desc select count(distinct a) from test.t;
- 默认值：`OFF`
- 该变量控制是否开启[跨数据库绑定执行计划](/sql-plan-management.md#跨数据库绑定执行计划-cross-db-binding)功能。

### `tidb_opt_enable_no_decorrelate_in_select` <span class="version-mark">从 v8.5.4 和 v9.0.0 版本开始引入</span>

- 作用域：SESSION | GLOBAL
- 是否持久化到集群：是
- 是否受 Hint [SET_VAR](/optimizer-hints.md#set_varvar_namevar_value) 控制：是
- 类型：布尔型
- 默认值：`OFF`
- 该变量控制优化器是否对 `SELECT` 列表中包含子查询的所有查询应用 [`NO_DECORRELATE()`](/optimizer-hints.md#no_decorrelate) Hint。

### `tidb_opt_enable_semi_join_rewrite` <span class="version-mark">从 v8.5.4 和 v9.0.0 版本开始引入</span>

- 作用域：SESSION | GLOBAL
- 是否持久化到集群：是
- 是否受 Hint [SET_VAR](/optimizer-hints.md#set_varvar_namevar_value) 控制：否
- 类型：布尔型
- 默认值：`OFF`
- 该变量控制优化器是否对包含子查询的所有查询应用 [`SEMI_JOIN_REWRITE()`](/optimizer-hints.md#semi_join_rewrite) Hint。

### `tidb_opt_fix_control` <span class="version-mark">从 v6.5.3 和 v7.1.0 版本开始引入</span>

- 作用域：SESSION | GLOBAL
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