Simply using a partition_options clause with ALTER TABLE on a partitioned table repartitions the table according to the partitioning scheme defined by the partition_options. This clause always begins with PARTITION BY, and follows the same syntax and other rules as apply to the partition_options clause for CREATE TABLE (see Section 13.1.17, “CREATE TABLE Syntax”, for more detailed information), and can also be used to partition an existing table that is not already partitioned. For example, consider a (nonpartitioned) table defined as shown here:

CREATE TABLE t1 (
    id INT,
    year_col INT
);

This table can be partitioned by HASH, using the id column as the partitioning key, into 8 partitions by means of this statement:

ALTER TABLE t1
    PARTITION BY HASH(id)
    PARTITIONS 8;

The table that results from using an ALTER TABLE ... PARTITION BY statement must follow the same rules as one created using CREATE TABLE ... PARTITION BY. This includes the rules governing the relationship between any unique keys (including any primary key) that the table might have, and the column or columns used in the partitioning expression, as discussed in Section 18.5.1, “Partitioning Keys, Primary Keys, and Unique Keys”. The CREATE TABLE ... PARTITION BY rules for specifying the number of partitions also apply to ALTER TABLE ... PARTITION BY.

ALTER TABLE ... PARTITION BY became available in MySQL 5.1.6.

The partition_definition clause for ALTER TABLE ADD PARTITION supports the same options as the clause of the same name for the CREATE TABLE statement. (See Section 13.1.17, “CREATE TABLE Syntax”, for the syntax and description.) Suppose that you have the partitioned table created as shown here:

CREATE TABLE t1 (
    id INT,
    year_col INT
)
PARTITION BY RANGE (year_col) (
    PARTITION p0 VALUES LESS THAN (1991),
    PARTITION p1 VALUES LESS THAN (1995),
    PARTITION p2 VALUES LESS THAN (1999)
);

You can add a new partition p3 to this table for storing values less than 2002 as follows:

ALTER TABLE t1 ADD PARTITION (PARTITION p3 VALUES LESS THAN (2002));

DROP PARTITION can be used to drop one or more RANGE or LIST partitions. This statement cannot be used with HASH or KEY partitions; instead, use COALESCE PARTITION (see below). Any data that was stored in the dropped partitions named in the partition_names list is discarded. For example, given the table t1 defined previously, you can drop the partitions named p0 and p1 as shown here:

ALTER TABLE t1 DROP PARTITION p0, p1;

ADD PARTITION and DROP PARTITION do not currently support IF [NOT] EXISTS.

Renames of partitioned table are supported. You can rename individual partitions indirectly using ALTER TABLE ... REORGANIZE PARTITION; however, this operation makes a copy of the partition's data..

COALESCE PARTITION can be used with a table that is partitioned by HASH or KEY to reduce the number of partitions by number. Suppose that you have created table t2 using the following definition:

CREATE TABLE t2 (
    name VARCHAR (30),
    started DATE
)
PARTITION BY HASH( YEAR(started) )
PARTITIONS 6;

You can reduce the number of partitions used by t2 from 6 to 4 using the following statement:

ALTER TABLE t2 COALESCE PARTITION 2;

The data contained in the last number partitions will be merged into the remaining partitions. In this case, partitions 4 and 5 will be merged into the first 4 partitions (the partitions numbered 0, 1, 2, and 3).

To change some but not all the partitions used by a partitioned table, you can use REORGANIZE PARTITION. This statement can be used in several ways:

For more detailed information about and examples of ALTER TABLE ... REORGANIZE PARTITION statements, see Section 18.3.1, “Management of RANGE and LIST Partitions”.

Several additional options were introduced in MySQL 5.1.5 for providing partition maintenance and repair functionality analogous to that implemented for nonpartitioned tables by statements such as CHECK TABLE and REPAIR TABLE (which are also supported for partitioned tables, beginning with MySQL 5.1.27—see note at the end of this item). These include ANALYZE PARTITION, CHECK PARTITION, OPTIMIZE PARTITION, REBUILD PARTITION, and REPAIR PARTITION. Each of these options takes a partition_names clause consisting of one or more names of partitions, separated by commas. The partitions must already exist in the table to be altered. You can also use the ALL keyword in place of partition_names, in which case the statement acts on all partitions in the table. For more information and examples, see Section 18.3.3, “Maintenance of Partitions”.

Prior to MySQL 5.1.68, it was not safe to execute multiple concurrent REBUILD TABLE operations operations on partitioned tables, whether on the same or different tables. (Bug #14589559, Bug #66645)

Some MySQL storage engines, such as InnoDB, do not support per-partition optimization. For a partitioned table using such a storage engine, ALTER TABLE ... OPTIMIZE PARTITION rebuilds the entire table. This is a known issue. (Bug #42822) Beginning with MySQL 5.1.68, running this statement on such a table causes the entire table to rebuilt and analyzed, and an appropriate warning to be issued. (Bug #11751825)

To work around this problem, use the statements ALTER TABLE ... REBUILD PARTITION and ALTER TABLE ... ANALYZE PARTITION instead.

The ANALYZE PARTITION, CHECK PARTITION, OPTIMIZE PARTITION, and REPAIR PARTITION options were disabled in MySQL 5.1.24, and re-enabled in MySQL 5.1.27. (Bug #20129) They are not supported for tables which are not partitioned; beginning with MySQL 5.1.31, they are not permitted for such tables.

Beginning with MySQL 5.1.27, you can use the statements ANALYZE TABLE, CHECK TABLE, OPTIMIZE TABLE, and REPAIR TABLE on partitioned tables. See Section 13.7.2, “Table Maintenance Statements”, for more information.

REMOVE PARTITIONING was introduced in MySQL 5.1.8 for the purpose of removing a table's partitioning without otherwise affecting the table or its data. (Previously, this was done using the ENGINE option.) This option can be combined with other ALTER TABLE options such as those used to add, drop, or rename drop columns or indexes.

In MySQL 5.1.7 and earlier, using the ENGINE option with ALTER TABLE caused any partitioning that a table might have had to be removed. Beginning with MySQL 5.1.8, this option merely changes the storage engine used by the table and no longer affects partitioning in any way.