SHOW PLACEMENT FOR

SHOW PLACEMENT FOR 用于汇总所有放置策略 (placement policy)，并用统一的形式呈现特定表、数据库或分区的信息。

本语句返回结果中的 Scheduling_State 列标识了 Placement Driver (PD) 在当前对象上的调度进度，有以下可能的结果：

  • PENDING: PD 没有进行调度。可能的原因之一是放置规则虽然语法上正确，但集群拓扑并不满足。比如指定 FOLLOWERS=4 但只有 3 个可用作 follower 的 TiKV 实例。
  • INPROGRESS: PD 正在进行调度。
  • SCHEDULED: PD 调度完成。

语法图

ShowStmt

SHOW PLACEMENT FOR - 图1

ShowPlacementTarget

SHOW PLACEMENT FOR - 图2

1. ShowStmt ::=
2. "SHOW" "PLACEMENT" "FOR" ShowPlacementTarget

4. ShowPlacementTarget ::=
5. DatabaseSym DBName
6. |   "TABLE" TableName
7. |   "TABLE" TableName "PARTITION" Identifier

示例

1. CREATE PLACEMENT POLICY p1 PRIMARY_REGION="us-east-1" REGIONS="us-east-1,us-west-1" FOLLOWERS=4;
2. use test;
3. ALTER DATABASE test PLACEMENT POLICY=p1;
4. CREATE TABLE t1 (a INT);
5. SHOW PLACEMENT FOR DATABASE test;
6. SHOW PLACEMENT FOR TABLE t1;
7. SHOW CREATE TABLE t1\G
8. CREATE TABLE t3 (a INT) PARTITION BY RANGE (a) (PARTITION p1 VALUES LESS THAN (10), PARTITION p2 VALUES LESS THAN (20));
9. SHOW PLACEMENT FOR TABLE t3 PARTITION p1\G

1. Query OK, 0 rows affected (0.02 sec)

3. Query OK, 0 rows affected (0.00 sec)

5. Query OK, 0 rows affected (0.01 sec)

7. +---------------+----------------------------------------------------------------------+------------------+
8. | Target        | Placement                                                            | Scheduling_State |
9. +---------------+----------------------------------------------------------------------+------------------+
10. | DATABASE test | PRIMARY_REGION="us-east-1" REGIONS="us-east-1,us-west-1" FOLLOWERS=4 | INPROGRESS       |
11. +---------------+----------------------------------------------------------------------+------------------+
12. 1 row in set (0.00 sec)

14. +---------------+-------------+------------------+
15. | Target        | Placement   | Scheduling_State |
16. +---------------+-------------+------------------+
17. | TABLE test.t1 | FOLLOWERS=4 | INPROGRESS       |
18. +---------------+-------------+------------------+
19. 1 row in set (0.00 sec)

21. ***************************[ 1. row ]***************************
22. Table        | t1
23. Create Table | CREATE TABLE `t1` (
24. `a` int(11) DEFAULT NULL
25. ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin /*T![placement] PLACEMENT POLICY=`p1` */
26. 1 row in set (0.00 sec)

28. ***************************[ 1. row ]***************************
29. Target           | TABLE test.t3 PARTITION p1
30. Placement        | PRIMARY_REGION="us-east-1" REGIONS="us-east-1,us-west-1" FOLLOWERS=4
31. Scheduling_State | PENDING
32. 1 row in set (0.00 sec)

MySQL 兼容性

该语句是 TiDB 对 MySQL 语法的扩展。

另请参阅