SHOW PLACEMENT
SHOW PLACEMENT 汇总了所有来自 placement policy 的放置选项，并以规范形式展示。
该语句返回的结果集中，Scheduling_State 字段表示 Placement Driver（PD）在调度放置规则时的当前进度：
PENDING：PD 尚未开始调度放置规则。这可能表示放置规则在语义上是正确的，但当前集群无法满足。例如，如果FOLLOWERS=4，但只有 3 个 TiKV 节点可作为 follower。INPROGRESS：PD 正在调度放置规则。SCHEDULED：PD 已成功调度放置规则。
语法
- ShowStmt
ShowStmt ::=
"SHOW" "PLACEMENT" ShowLikeOrWhere?
示例
CREATE PLACEMENT POLICY p1 PRIMARY_REGION="us-east-1" REGIONS="us-east-1,us-west-1" FOLLOWERS=4;
CREATE TABLE t1 (a INT) PLACEMENT POLICY=p1;
SHOW PLACEMENT;
Query OK, 0 rows affected (0.01 sec)
Query OK, 0 rows affected (0.00 sec)
+---------------+----------------------------------------------------------------------+------------------+
| Target | Placement | Scheduling_State |
+---------------+----------------------------------------------------------------------+------------------+
| POLICY p1 | PRIMARY_REGION="us-east-1" REGIONS="us-east-1,us-west-1" FOLLOWERS=4 | NULL |
| DATABASE test | PRIMARY_REGION="us-east-1" REGIONS="us-east-1,us-west-1" FOLLOWERS=4 | INPROGRESS |
| TABLE test.t1 | PRIMARY_REGION="us-east-1" REGIONS="us-east-1,us-west-1" FOLLOWERS=4 | INPROGRESS |
+---------------+----------------------------------------------------------------------+------------------+
4 rows in set (0.00 sec)
MySQL 兼容性
该语句是 TiDB 对 MySQL 语法的扩展。