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partition: global index GA & deprecated tidb_enable_table_partition, tidb_enable_list_partition and tidb_enable_global_index #18659

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partition: global index GA & deprecated tidb_enable_table_partition, tidb_enable_list_partition and tidb_enable_global_index #18659

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global index ga
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5 changes: 1 addition & 4 deletions partitioned-table.md
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Expand Up @@ -1680,10 +1680,6 @@ ERROR 1503 (HY000): A UNIQUE INDEX must include all columns in the table's parti

为解决这些问题，TiDB 从 v8.3.0 开始引入全局索引。全局索引能覆盖整个表的数据，使得主键和唯一键在不包含分区键的情况下仍能保持全局唯一性。同时，全局索引可以在一次操作中访问多个分区的数据，显著提升了针对非分区键的查询性能。

> **警告：**
>
> 全局索引目前为实验特性，不建议在生产环境中使用。该功能可能会在未事先通知的情况下发生变化或删除。如果发现 bug，请在 GitHub 上提 [issue](https://github.com/pingcap/tidb/issues) 反馈。

如果你需要创建的唯一索引**不包含分区表达式中使用的所有列**，可以通过启用 [`tidb_enable_global_index`](/system-variables.md#tidb_enable_global_index-从-v760-版本开始引入) 系统变量并在索引定义中添加 `GLOBAL` 关键字来实现。

> **注意：**
Expand Down Expand Up @@ -1774,6 +1770,7 @@ ALTER TABLE t1 PARTITION BY HASH (col1) PARTITIONS 3 UPDATE INDEXES (uidx12 LOCA
- `GLOBAL` 和 `LOCAL` 关键字仅适用于分区表，对非分区表没有影响。即在非分区表中，全局索引和局部索引之间没有区别。
- DDL 操作如 `ADD PARTITION`、`DROP PARTITION`、`TRUNCATE PARTITION`、`REORGANIZE PARTITION`、`SPLIT PARTITION` 和 `EXCHANGE PARTITION` 等也会触发对全局索引的更新，这些 DDL 的执行结果将在全局索引更新完成后才会返回。因此，这可能会延迟一些通常需要快速完成的 DDL 的操作，如数据归档操作（`EXCHANGE PARTITION`、`TRUNCATE PARTITION` 和 `DROP PARTITION`）。而如果没有全局索引，这些 DDL 操作可以立即执行完成。
- 默认情况下，分区表的主键为聚簇索引，且必须包含分区键。如果要求主键不包含分区建，可以在建表时显式指定主键为非聚簇的全局索引，例如：`PRIMARY KEY(col1, col2) NONCLUSTERED GLOBAL`。
- 如果在表达式列上添加了全局索引，该全局索引需要手动收集统计信息。
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### 关于函数的分区限制

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4 changes: 0 additions & 4 deletions system-variables.md
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Expand Up @@ -1935,10 +1935,6 @@ mysql> SELECT job_info FROM mysql.analyze_jobs ORDER BY end_time DESC LIMIT 1;

### `tidb_enable_global_index` <span class="version-mark">从 v7.6.0 版本开始引入</span>

> **警告：**
>
> 该变量控制的功能为实验特性，不建议在生产环境中使用。该功能可能会在未事先通知的情况下发生变化或删除。如果发现 bug，请在 GitHub 上提 [issue](https://github.com/pingcap/tidb/issues) 反馈。

- 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
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