DROP PLACEMENT POLICY
DROP PLACEMENT POLICY is used to drop a previously created placement policy.
Synopsis
- DropPolicyStmt
- PolicyName
DropPolicyStmt ::=
"DROP" "PLACEMENT" "POLICY" IfExists PolicyName
PolicyName ::=
Identifier
Examples
Placement policies can only be dropped when they are not referenced by any tables or partitions.
CREATE PLACEMENT POLICY p1 FOLLOWERS=4;
CREATE TABLE t1 (a INT PRIMARY KEY) PLACEMENT POLICY=p1;
DROP PLACEMENT POLICY p1; -- This statement fails because the placement policy p1 is referenced.
-- Finds which tables and partitions reference the placement policy.
SELECT table_schema, table_name FROM information_schema.tables WHERE tidb_placement_policy_name='p1';
SELECT table_schema, table_name FROM information_schema.partitions WHERE tidb_placement_policy_name='p1';
ALTER TABLE t1 PLACEMENT POLICY=default; -- Removes the placement policy from t1.
DROP PLACEMENT POLICY p1; -- Succeeds.
Query OK, 0 rows affected (0.10 sec)
Query OK, 0 rows affected (0.11 sec)
ERROR 8241 (HY000): Placement policy 'p1' is still in use
+--------------+------------+
| table_schema | table_name |
+--------------+------------+
| test | t1 |
+--------------+------------+
1 row in set (0.00 sec)
Empty set (0.01 sec)
Query OK, 0 rows affected (0.08 sec)
Query OK, 0 rows affected (0.21 sec)
MySQL compatibility
This statement is a TiDB extension to MySQL syntax.