MySQL 8 Administrator???s Guide

HASH and KEY partition management

Table partitions of the HASH or KEY types are similar compared to table partitioning by the RANGE or LIST types of partitioning. Dropping a partition is not applicable if a table is partitioned by the HASH or KEY type of partitioning, but there is option for merging HASH or KEY partitions, using ALTER TABLE ... COALESCE PARTITION.

Consider if you have client table data partitioned by HASH partitioning, divided in twelve partitions as follows:

CREATE TABLE client (    client_id INT,    first_name VARCHAR(25),    last_name VARCHAR(25),    signed DATE)PARTITION BY HASH (MONTH (signed))PARTITIONS 12;

In the preceding table partitioning schema, if you want to reduce the number of partitions to eight instead of twelve, use ...