MySQL 9.1 Release Notes
If the total length of the
DELETE statement for
related_table is more than the default
value of the
max_allowed_packet system
variable, you should split it into smaller parts and execute
multiple DELETE statements. You
probably get the fastest DELETE
by specifying only 100 to 1,000
related_column values per statement if the
related_column is indexed. If the
related_column is not indexed, the speed is
independent of the number of arguments in the
IN clause.