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MySQL 8.0 Reference Manual

26.2.6 Subpartitioning

Subpartitioning—also known ascomposite partitioning—is the further division of each partition in a partitioned table. Consider the followingCREATE TABLE statement:

CREATE TABLE ts (id INT, purchased DATE)    PARTITION BY RANGE( YEAR(purchased) )    SUBPARTITION BY HASH( TO_DAYS(purchased) )    SUBPARTITIONS 2 (        PARTITION p0 VALUES LESS THAN (1990),        PARTITION p1 VALUES LESS THAN (2000),        PARTITION p2 VALUES LESS THAN MAXVALUE    );

Tablets has 3RANGE partitions. Each of these partitions—p0,p1, andp2—is further divided into 2 subpartitions. In effect, the entire table is divided into3 * 2 = 6 partitions. However, due to the action of thePARTITION BY RANGE clause, the first 2 of these store only those records with a value less than 1990 in thepurchased column.

It is possible to subpartition tables that are partitioned byRANGE orLIST. Subpartitions may use eitherHASH orKEY partitioning. This is also known ascomposite partitioning.

Note

SUBPARTITION BY HASH andSUBPARTITION BY KEY generally follow the same syntax rules asPARTITION BY HASH andPARTITION BY KEY, respectively. An exception to this is thatSUBPARTITION BY KEY (unlikePARTITION BY KEY) does not currently support a default column, so the column used for this purpose must be specified, even if the table has an explicit primary key. This is a known issue which we are working to address; seeIssues with subpartitions, for more information and an example.

It is also possible to define subpartitions explicitly usingSUBPARTITION clauses to specify options for individual subpartitions. For example, a more verbose fashion of creating the same tablets as shown in the previous example would be:

CREATE TABLE ts (id INT, purchased DATE)    PARTITION BY RANGE( YEAR(purchased) )    SUBPARTITION BY HASH( TO_DAYS(purchased) ) (        PARTITION p0 VALUES LESS THAN (1990) (            SUBPARTITION s0,            SUBPARTITION s1        ),        PARTITION p1 VALUES LESS THAN (2000) (            SUBPARTITION s2,            SUBPARTITION s3        ),        PARTITION p2 VALUES LESS THAN MAXVALUE (            SUBPARTITION s4,            SUBPARTITION s5        )    );

Some syntactical items of note are listed here:

Each partition must have the same number of subpartitions.

If you explicitly define any subpartitions usingSUBPARTITION on any partition of a partitioned table, you must define them all. In other words, the following statement fails:

CREATE TABLE ts (id INT, purchased DATE)    PARTITION BY RANGE( YEAR(purchased) )    SUBPARTITION BY HASH( TO_DAYS(purchased) ) (        PARTITION p0 VALUES LESS THAN (1990) (            SUBPARTITION s0,            SUBPARTITION s1        ),        PARTITION p1 VALUES LESS THAN (2000),        PARTITION p2 VALUES LESS THAN MAXVALUE (            SUBPARTITION s2,            SUBPARTITION s3        )    );

This statement would still fail even if it usedSUBPARTITIONS 2.

EachSUBPARTITION clause must include (at a minimum) a name for the subpartition. Otherwise, you may set any desired option for the subpartition or allow it to assume its default setting for that option.

Subpartition names must be unique across the entire table. For example, the followingCREATE TABLE statement is valid:

CREATE TABLE ts (id INT, purchased DATE)    PARTITION BY RANGE( YEAR(purchased) )    SUBPARTITION BY HASH( TO_DAYS(purchased) ) (        PARTITION p0 VALUES LESS THAN (1990) (            SUBPARTITION s0,            SUBPARTITION s1        ),        PARTITION p1 VALUES LESS THAN (2000) (            SUBPARTITION s2,            SUBPARTITION s3        ),        PARTITION p2 VALUES LESS THAN MAXVALUE (            SUBPARTITION s4,            SUBPARTITION s5        )    );

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