26.3 Partition Management

26.3.1 Management of RANGE and LIST Partitions

26.3.2 Management of HASH and KEY Partitions

26.3.3 Exchanging Partitions and Subpartitions with Tables

26.3.4 Maintenance of Partitions

26.3.5 Obtaining Information About Partitions

There are a number of ways using SQL statements to modify partitioned tables; it is possible to add, drop, redefine, merge, or split existing partitions using the partitioning extensions to the ALTER TABLE statement. There are also ways to obtain information about partitioned tables and partitions. We discuss these topics in the sections that follow.

• For information about partition management in tables partitioned by RANGE or LIST, see Section 26.3.1, “Management of RANGE and LIST Partitions”.

• For a discussion of managing HASH and KEY partitions, see Section 26.3.2, “Management of HASH and KEY Partitions”.

• See Section 26.3.5, “Obtaining Information About Partitions”, for a discussion of mechanisms provided in MySQL 9.1 for obtaining information about partitioned tables and partitions.

• For a discussion of performing maintenance operations on partitions, see Section 26.3.4, “Maintenance of Partitions”.

Note

All partitions of a partitioned table must have the same number of subpartitions; it is not possible to change the subpartitioning once the table has been created.

To change a table's partitioning scheme, it is necessary only to use the ALTER TABLE statement with a partition_options option, which has the same syntax as that as used with CREATE TABLE for creating a partitioned table; this option (also) always begins with the keywords PARTITION BY. Suppose that the following CREATE TABLE statement was used to create a table that is partitioned by range:

CREATE TABLE trb3 (id INT, name VARCHAR(50), purchased DATE)
    PARTITION BY RANGE( YEAR(purchased) ) (
        PARTITION p0 VALUES LESS THAN (1990),
        PARTITION p1 VALUES LESS THAN (1995),
        PARTITION p2 VALUES LESS THAN (2000),
        PARTITION p3 VALUES LESS THAN (2005)
    );

To repartition this table so that it is partitioned by key into two partitions using the id column value as the basis for the key, you can use this statement:

ALTER TABLE trb3 PARTITION BY KEY(id) PARTITIONS 2;

This has the same effect on the structure of the table as dropping the table and re-creating it using CREATE TABLE trb3 PARTITION BY KEY(id) PARTITIONS 2;.

ALTER TABLE ... ENGINE [=] ... changes only the storage engine used by the table, and leaves the table's partitioning scheme intact. The statement succeeds only if the target storage engine provides partitioning support. You can use ALTER TABLE ... REMOVE PARTITIONING to remove a table's partitioning; see Section 15.1.9, “ALTER TABLE Statement”.

Important

Only a single PARTITION BY, ADD PARTITION, DROP PARTITION, REORGANIZE PARTITION, or COALESCE PARTITION clause can be used in a given ALTER TABLE statement. If you (for example) wish to drop a partition and reorganize a table's remaining partitions, you must do so in two separate ALTER TABLE statements (one using DROP PARTITION and then a second one using REORGANIZE PARTITION).

You can delete all rows from one or more selected partitions using ALTER TABLE ... TRUNCATE PARTITION.