CREATE INDEX

Syntax

CREATE [OR REPLACE] [UNIQUE|FULLTEXT|SPATIAL] INDEX 
  [IF NOT EXISTS] index_name
    [index_type]
    ON tbl_name (index_col_name,...)
    [WAIT n | NOWAIT]
    [index_option]
    [algorithm_option | lock_option] ...

index_col_name:
    col_name [(length)] [ASC | DESC]

index_type:
    USING {BTREE | HASH | RTREE}

index_option:
    [ KEY_BLOCK_SIZE [=] value
  | index_type
  | WITH PARSER parser_name
  | COMMENT 'string'
  | CLUSTERING={YES| NO} ]
  [ IGNORED | NOT IGNORED ]

algorithm_option:
    ALGORITHM [=] {DEFAULT|INPLACE|COPY|NOCOPY|INSTANT}

lock_option:
    LOCK [=] {DEFAULT|NONE|SHARED|EXCLUSIVE}

Description

The CREATE INDEX statement is used to add indexes to a table. Indexes can be created at the same as the table, with the CREATE TABLE statement. In some cases, such as for InnoDB primary keys, doing so during creation is preferable, as adding a primary key will involve rebuilding the table.

The statement is mapped to an ALTER TABLE statement to create indexes. See ALTER TABLE. CREATE INDEX cannot be used to create a PRIMARY KEY; use ALTER TABLE instead.

If another connection is using the table, a metadata lock is active, and this statement will wait until the lock is released. This is also true for non-transactional tables.

Another shortcut, DROP INDEX, allows the removal of an index.

For valid identifiers to use as index names, see Identifier Names.

For limits on InnoDB indexes, see InnoDB Limitations.

Privileges

Executing the CREATE INDEX statement requires the INDEX privilege for the table or the database.

Online DDL

Online DDL is supported with the ALGORITHM and LOCK clauses.

See InnoDB Online DDL Overview for more information on online DDL with InnoDB.

CREATE OR REPLACE INDEX

If the OR REPLACE clause is used and if the index already exists, then instead of returning an error, the server will drop the existing index and replace it with the newly defined index.

CREATE INDEX IF NOT EXISTS

If the IF NOT EXISTS clause is used, then the index will only be created if an index with the same name does not already exist. If the index already exists, then a warning will be triggered by default.

Index Definitions

See CREATE TABLE: Index Definitions for information about index definitions.

WAIT/NOWAIT

Set the lock wait timeout. See WAIT and NOWAIT.

ALGORITHM

See ALTER TABLE: ALGORITHM for more information.

LOCK

See ALTER TABLE: LOCK for more information.

Progress Reporting

MariaDB provides progress reporting for CREATE INDEX statement for clients that support the new progress reporting protocol. For example, if you were using the mariadb client, then the progress report might look like this::

CREATE INDEX i ON tab (num);
Stage: 1 of 2 'copy to tmp table'    46% of stage

The progress report is also shown in the output of the SHOW PROCESSLIST statement and in the contents of the information_schema.PROCESSLIST table.

See Progress Reporting for more information.

WITHOUT OVERLAPS

Examples

Creating a unique index:

CREATE UNIQUE INDEX HomePhone ON Employees(Home_Phone);

OR REPLACE and IF NOT EXISTS:

CREATE INDEX xi ON xx5 (x);
Query OK, 0 rows affected (0.03 sec)

CREATE INDEX xi ON xx5 (x);
ERROR 1061 (42000): Duplicate key name 'xi'

CREATE OR REPLACE INDEX xi ON xx5 (x);
Query OK, 0 rows affected (0.03 sec)

CREATE INDEX IF NOT EXISTS xi ON xx5 (x);
Query OK, 0 rows affected, 1 warning (0.00 sec)

SHOW WARNINGS;
+-------+------+-------------------------+
| Level | Code | Message                 |
+-------+------+-------------------------+
| Note  | 1061 | Duplicate key name 'xi' |
+-------+------+-------------------------+

From MariaDB 10.5.3, creating a unique index for an application-time period table with a WITHOUT OVERLAPS constraint:

CREATE UNIQUE INDEX u ON rooms (room_number, p WITHOUT OVERLAPS);

See Also

• Identifier Names
• Getting Started with Indexes
• What is an Index?
• ALTER TABLE
• DROP INDEX
• SHOW INDEX
• SPATIAL INDEX
• Full-text Indexes
• WITHOUT OVERLAPS
• Ignored Indexes
• InnoDB Limitations