If the data has crossed the retention, you can DROP the whole partition, which is superquick compared with conventional DELETE FROM TABLE statement. This is very helpful in archiving the data efficiently.
If p20170930 has crossed the retention, you can DROP the partition using the ALTER TABLE ... DROP PARTITION statement:
mysql> ALTER TABLE event_history DROP PARTITION p20170930;Query OK, 0 rows affected (0.02 sec)Records: 0 Duplicates: 0 Warnings: 0
Dropping the partition removes the PARTITION DEFINITION from the table.
