ADD INDEX
The ALTER TABLE.. ADD INDEX statement adds an index to an existing table. This operation is online in TiDB, which means that neither reads or writes to the table are blocked by adding an index.
Synopsis
- AlterTableStmt
- AlterTableSpec
- Constraint
- ConstraintKeywordOpt
- ConstraintElem
- IndexNameAndTypeOpt
- IndexPartSpecificationList
- IndexPartSpecification
- IndexOptionList
- IndexOption
- KeyOrIndex
- IndexKeyTypeOpt
- IndexInvisible
- IndexTypeName
AlterTableStmt ::=
'ALTER' IgnoreOptional 'TABLE' TableName ( AlterTableSpecListOpt AlterTablePartitionOpt | 'ANALYZE' 'PARTITION' PartitionNameList ( 'INDEX' IndexNameList )? AnalyzeOptionListOpt )
AlterTableSpec ::=
TableOptionList
| 'SET' 'TIFLASH' 'REPLICA' LengthNum LocationLabelList
| 'CONVERT' 'TO' CharsetKw ( CharsetName | 'DEFAULT' ) OptCollate
| 'ADD' ( ColumnKeywordOpt IfNotExists ( ColumnDef ColumnPosition | '(' TableElementList ')' ) | Constraint | 'PARTITION' IfNotExists NoWriteToBinLogAliasOpt ( PartitionDefinitionListOpt | 'PARTITIONS' NUM ) )
| ( ( 'CHECK' | 'TRUNCATE' ) 'PARTITION' | ( 'OPTIMIZE' | 'REPAIR' | 'REBUILD' ) 'PARTITION' NoWriteToBinLogAliasOpt ) AllOrPartitionNameList
| 'COALESCE' 'PARTITION' NoWriteToBinLogAliasOpt NUM
| 'DROP' ( ColumnKeywordOpt IfExists ColumnName RestrictOrCascadeOpt | 'PRIMARY' 'KEY' | 'PARTITION' IfExists PartitionNameList | ( KeyOrIndex IfExists | 'CHECK' ) Identifier | 'FOREIGN' 'KEY' IfExists Symbol )
| 'EXCHANGE' 'PARTITION' Identifier 'WITH' 'TABLE' TableName WithValidationOpt
| ( 'IMPORT' | 'DISCARD' ) ( 'PARTITION' AllOrPartitionNameList )? 'TABLESPACE'
| 'REORGANIZE' 'PARTITION' NoWriteToBinLogAliasOpt ReorganizePartitionRuleOpt
| 'ORDER' 'BY' AlterOrderItem ( ',' AlterOrderItem )*
| ( 'DISABLE' | 'ENABLE' ) 'KEYS'
| ( 'MODIFY' ColumnKeywordOpt IfExists | 'CHANGE' ColumnKeywordOpt IfExists ColumnName ) ColumnDef ColumnPosition
| 'ALTER' ( ColumnKeywordOpt ColumnName ( 'SET' 'DEFAULT' ( SignedLiteral | '(' Expression ')' ) | 'DROP' 'DEFAULT' ) | 'CHECK' Identifier EnforcedOrNot | 'INDEX' Identifier IndexInvisible )
| 'RENAME' ( ( 'COLUMN' | KeyOrIndex ) Identifier 'TO' Identifier | ( 'TO' | '='? | 'AS' ) TableName )
| LockClause
| AlgorithmClause
| 'FORCE'
| ( 'WITH' | 'WITHOUT' ) 'VALIDATION'
| 'SECONDARY_LOAD'
| 'SECONDARY_UNLOAD'
Constraint ::=
ConstraintKeywordOpt ConstraintElem
ConstraintKeywordOpt ::=
( 'CONSTRAINT' Symbol? )?
ConstraintElem ::=
( ( 'PRIMARY' 'KEY' | KeyOrIndex IfNotExists | 'UNIQUE' KeyOrIndexOpt ) IndexNameAndTypeOpt | 'FULLTEXT' KeyOrIndexOpt IndexName ) '(' IndexPartSpecificationList ')' IndexOptionList
| 'FOREIGN' 'KEY' IfNotExists IndexName '(' IndexPartSpecificationList ')' ReferDef
| 'CHECK' '(' Expression ')' EnforcedOrNotOpt
IndexNameAndTypeOpt ::=
IndexName ( 'USING' IndexTypeName )?
| Identifier 'TYPE' IndexTypeName
IndexPartSpecificationList ::=
IndexPartSpecification ( ',' IndexPartSpecification )*
IndexPartSpecification ::=
( ColumnName OptFieldLen | '(' Expression ')' ) Order
IndexOptionList ::=
IndexOption*
IndexOption ::=
'KEY_BLOCK_SIZE' '='? LengthNum
| IndexType
| 'WITH' 'PARSER' Identifier
| 'COMMENT' stringLit
| IndexInvisible
KeyOrIndex ::=
'KEY'
| 'INDEX'
IndexKeyTypeOpt ::=
( 'UNIQUE' | 'SPATIAL' | 'FULLTEXT' )?
IndexInvisible ::=
'VISIBLE'
| 'INVISIBLE'
IndexTypeName ::=
'BTREE'
| 'HASH'
| 'RTREE'
Examples
mysql> CREATE TABLE t1 (id INT NOT NULL PRIMARY KEY AUTO_INCREMENT, c1 INT NOT NULL);
Query OK, 0 rows affected (0.11 sec)
mysql> INSERT INTO t1 (c1) VALUES (1),(2),(3),(4),(5);
Query OK, 5 rows affected (0.03 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> ALTER TABLE t1 ADD INDEX (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 compatibility
FULLTEXT,HASHandSPATIALindexes are not supported.- Descending indexes are not supported (similar to MySQL 5.7).
- Adding multiple indexes at the same time is currently not supported.
- Adding the primary key of the
CLUSTEREDtype to a table is not supported. For more details about the primary key of theCLUSTEREDtype, refer to clustered index.