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DROP INDEX

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

Synopsis

AlterTableDropIndexStmt
ALTERIgnoreOptionalTABLEAlterTableDropIndexSpec
IgnoreOptional
IGNORE
TableName
Identifier.Identifier
AlterTableDropIndexSpec
DROPKeyOrIndexFOREIGNKEYIfExistsIdentifier
KeyOrIndex
KEYINDEX
IfExists
IFEXISTS

Examples

mysql> CREATE TABLE t1 (id INT NOT NULL PRIMARY KEY AUTO_INCREMENT, c1 INT NOT NULL); Query OK, 0 rows affected (0.10 sec) mysql> INSERT INTO t1 (c1) VALUES (1),(2),(3),(4),(5); Query OK, 5 rows affected (0.02 sec) Records: 5 Duplicates: 0 Warnings: 0 mysql> EXPLAIN SELECT * FROM t1 WHERE c1 = 3; +-------------------------+----------+-----------+---------------+--------------------------------+ | id | estRows | task | access object | operator info | +-------------------------+----------+-----------+---------------+--------------------------------+ | TableReader_7 | 10.00 | root | | data:Selection_6 | | └─Selection_6 | 10.00 | cop[tikv] | | eq(test.t1.c1, 3) | | └─TableFullScan_5 | 10000.00 | cop[tikv] | table:t1 | keep order:false, stats:pseudo | +-------------------------+----------+-----------+---------------+--------------------------------+ 3 rows in set (0.00 sec) mysql> CREATE INDEX c1 ON t1 (c1); Query OK, 0 rows affected (0.30 sec) mysql> EXPLAIN SELECT * FROM t1 WHERE c1 = 3; +------------------------+---------+-----------+------------------------+---------------------------------------------+ | id | estRows | task | access object | operator info | +------------------------+---------+-----------+------------------------+---------------------------------------------+ | IndexReader_6 | 0.01 | root | | index:IndexRangeScan_5 | | └─IndexRangeScan_5 | 0.01 | cop[tikv] | table:t1, index:c1(c1) | range:[3,3], keep order:false, stats:pseudo | +------------------------+---------+-----------+------------------------+---------------------------------------------+ 2 rows in set (0.00 sec) mysql> ALTER TABLE t1 DROP INDEX c1; Query OK, 0 rows affected (0.30 sec)

MySQL compatibility

  • Removing the primary key constraint from a column is not supported by default. You can enable the feature by setting the alter-primary-key configuration item to true. For details, see alter-primary-key.

See also

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