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
- ShowPlacementTarget
ShowStmt ::=
"PLACEMENT" "FOR" ShowPlacementTarget
ShowPlacementTarget ::=
DatabaseSym DBName
| "TABLE" TableName
| "TABLE" TableName "PARTITION" Identifier
示例
CREATE PLACEMENT POLICY p1 PRIMARY_REGION="us-east-1" REGIONS="us-east-1,us-west-1" FOLLOWERS=4;
use test;
ALTER DATABASE test PLACEMENT POLICY=p1;
CREATE TABLE t1 (a INT);
SHOW PLACEMENT FOR DATABASE test;
SHOW PLACEMENT FOR TABLE t1;
SHOW CREATE TABLE t1\G;
CREATE TABLE t3 (a INT) PARTITION BY RANGE (a) (PARTITION p1 VALUES LESS THAN (10), PARTITION p2 VALUES LESS THAN (20));
SHOW PLACEMENT FOR TABLE t3 PARTITION p1\G;
Query OK, 0 rows affected (0.02 sec)
Query OK, 0 rows affected (0.00 sec)
Query OK, 0 rows affected (0.01 sec)
+---------------+----------------------------------------------------------------------+------------------+
| Target | Placement | Scheduling_State |
+---------------+----------------------------------------------------------------------+------------------+
| DATABASE test | PRIMARY_REGION="us-east-1" REGIONS="us-east-1,us-west-1" FOLLOWERS=4 | INPROGRESS |
+---------------+----------------------------------------------------------------------+------------------+
1 row in set (0.00 sec)
+---------------+-------------+------------------+
| Target | Placement | Scheduling_State |
+---------------+-------------+------------------+
| TABLE test.t1 | FOLLOWERS=4 | INPROGRESS |
+---------------+-------------+------------------+
1 row in set (0.00 sec)
***************************[ 1. row ]***************************
Table | t1
Create Table | CREATE TABLE `t1` (
`a` int(11) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin /*T![placement] PLACEMENT POLICY=`p1` */
1 row in set (0.00 sec)
***************************[ 1. row ]***************************
Target | TABLE test.t3 PARTITION p1
Placement | PRIMARY_REGION="us-east-1" REGIONS="us-east-1,us-west-1" FOLLOWERS=4
Scheduling_State | PENDING
1 row in set (0.00 sec)
MySQL 兼容性
该语句是 TiDB 对 MySQL 语法的扩展。