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Migrate contributor PRs with pending CLA (#4771)
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TomShawn authored Nov 2, 2020
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2 changes: 1 addition & 1 deletion sql-logical-optimization.md
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Expand Up @@ -5,7 +5,7 @@ aliases: ['/docs-cn/dev/sql-logical-optimization/']

# 逻辑优化

本章节将对一些比较关键的逻辑改写进行说明,帮助大家理解 TiDB 如何生成最终的查询计划。比如在 TiDB 输入 `select * from t where t.a in (select * from t1 where t1.b=t.b)` 这个查询时,在最终的执行计划中将看不到这个 `t.a in (select t1.a from t1 where t1.b=t.b` 这个 `IN` 子查询的存在,这便是因为 TiDB 对这里进行了一些改写。
本章节将对一些比较关键的逻辑改写进行说明,帮助大家理解 TiDB 如何生成最终的查询计划。比如在 TiDB 输入 `select * from t where t.a in (select t1.a from t1 where t1.b=t.b)` 这个查询时,在最终的执行计划中将看不到这个 `t.a in (select t1.a from t1 where t1.b=t.b)` 这个 `IN` 子查询的存在,这便是因为 TiDB 对这里进行了一些改写。

本章节会介绍如下几个关键改写:

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2 changes: 1 addition & 1 deletion system-variables.md
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Expand Up @@ -722,7 +722,7 @@ set tidb_query_log_max_len = 20;

### `tidb_skip_isolation_level_check`

- 作用域:SESSION
- 作用域:SESSION | GLOBAL

- 默认值:0

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