DROP INDEX

DROP INDEX 语句用于从指定的表中删除索引，并在 TiKV 中将空间标记为释放。

语法图

1. DropIndexStmt ::=
2. "DROP" "INDEX" IfExists Identifier "ON" TableName IndexLockAndAlgorithmOpt

4. IfExists ::=
5. ( 'IF' 'EXISTS' )?

7. IndexLockAndAlgorithmOpt ::=
8. ( LockClause AlgorithmClause? | AlgorithmClause LockClause? )?

示例

1. CREATE TABLE t1 (id INT NOT NULL PRIMARY KEY AUTO_INCREMENT, c1 INT NOT NULL);

1. Query OK, 0 rows affected (0.10 sec)

1. INSERT INTO t1 (c1) VALUES (1),(2),(3),(4),(5);

1. Query OK, 5 rows affected (0.02 sec)
2. Records: 5  Duplicates: 0  Warnings: 0

1. EXPLAIN SELECT * FROM t1 WHERE c1 = 3;

1. +-------------------------+----------+-----------+---------------+--------------------------------+
2. | id                      | estRows  | task      | access object | operator info                  |
3. +-------------------------+----------+-----------+---------------+--------------------------------+
4. | TableReader_7           | 10.00    | root      |               | data:Selection_6               |
5. | └─Selection_6           | 10.00    | cop[tikv] |               | eq(test.t1.c1, 3)              |
6. |   └─TableFullScan_5     | 10000.00 | cop[tikv] | table:t1      | keep order:false, stats:pseudo |
7. +-------------------------+----------+-----------+---------------+--------------------------------+
8. 3 rows in set (0.00 sec)

1. CREATE INDEX c1 ON t1 (c1);

1. Query OK, 0 rows affected (0.30 sec)

1. EXPLAIN SELECT * FROM t1 WHERE c1 = 3;

1. +------------------------+---------+-----------+------------------------+---------------------------------------------+
2. | id                     | estRows | task      | access object          | operator info                               |
3. +------------------------+---------+-----------+------------------------+---------------------------------------------+
4. | IndexReader_6          | 0.01    | root      |                        | index:IndexRangeScan_5                      |
5. | └─IndexRangeScan_5     | 0.01    | cop[tikv] | table:t1, index:c1(c1) | range:[3,3], keep order:false, stats:pseudo |
6. +------------------------+---------+-----------+------------------------+---------------------------------------------+
7. 2 rows in set (0.00 sec)

1. DROP INDEX c1 ON t1;

1. Query OK, 0 rows affected (0.30 sec)

MySQL 兼容性

  • 不支持删除 CLUSTERED 类型的 PRIMARY KEY。要了解关于 CLUSTERED 主键的详细信息，请参考聚簇索引。

另请参阅