DROP INDEX

This statement removes an index from a specified table, marking space as free in TiKV.

Synopsis

DropIndexStmt

DROP INDEX - 图1

IfExists

DROP INDEX - 图2

IndexLockAndAlgorithmOpt

DROP INDEX - 图3

  1. DropIndexStmt ::=
  2.     "DROP" "INDEX" IfExists Identifier "ON" TableName IndexLockAndAlgorithmOpt
  4. IfExists ::=
  5.     ( 'IF' 'EXISTS' )?
  7. IndexLockAndAlgorithmOpt ::=
  8.     ( LockClause AlgorithmClause? | AlgorithmClause LockClause? )?

Examples

  1. mysql> CREATE TABLE t1 (id INT NOT NULL PRIMARY KEY AUTO_INCREMENT, c1 INT NOT NULL);
  2. Query OK, 0 rows affected (0.10 sec)
  4. mysql> INSERT INTO t1 (c1) VALUES (1),(2),(3),(4),(5);
  5. Query OK, 5 rows affected (0.02 sec)
  6. Records: 5  Duplicates: 0  Warnings: 0
  8. mysql> EXPLAIN SELECT * FROM t1 WHERE c1 = 3;
  9. +-------------------------+----------+-----------+---------------+--------------------------------+
  10. | id                      | estRows  | task      | access object | operator info                  |
  11. +-------------------------+----------+-----------+---------------+--------------------------------+
  12. | TableReader_7           | 10.00    | root      |               | data:Selection_6               |
  13. | └─Selection_6           | 10.00    | cop[tikv] |               | eq(test.t1.c1, 3)              |
  14. |   └─TableFullScan_5     | 10000.00 | cop[tikv] | table:t1      | keep order:false, stats:pseudo |
  15. +-------------------------+----------+-----------+---------------+--------------------------------+
  16. 3 rows in set (0.00 sec)
  18. mysql> CREATE INDEX c1 ON t1 (c1);
  19. Query OK, 0 rows affected (0.30 sec)
  21. mysql> EXPLAIN SELECT * FROM t1 WHERE c1 = 3;
  22. +------------------------+---------+-----------+------------------------+---------------------------------------------+
  23. | id                     | estRows | task      | access object          | operator info                               |
  24. +------------------------+---------+-----------+------------------------+---------------------------------------------+
  25. | IndexReader_6          | 0.01    | root      |                        | index:IndexRangeScan_5                      |
  26. | └─IndexRangeScan_5     | 0.01    | cop[tikv] | table:t1, index:c1(c1) | range:[3,3], keep order:false, stats:pseudo |
  27. +------------------------+---------+-----------+------------------------+---------------------------------------------+
  28. 2 rows in set (0.00 sec)
  30. mysql> DROP INDEX c1 ON t1;
  31. Query OK, 0 rows affected (0.30 sec)

MySQL compatibility

  • Dropping the primary key of the CLUSTERED type is not supported. For more details about the primary key of the CLUSTERED type, refer to clustered index.

See also