MDEV-16329, the majority of ALTER TABLE operations would be possible while allowing concurrent modifications to the table. Notable exceptions include ADD … AUTO_INCREMENT and DROP PRIMARY KEY without ADD PRIMARY KEY.
It could be convenient to introduce an option that allows ALTER TABLE to behave like ALTER ONLINE TABLE: refuse the operation if it would lock the table. This would be in line with the SET alter_algorithm that was introduced in
MDEV-13134: allow table-rebuilding or non-instantaneous ALTER TABLE to be refused unless an explicit ALGORITHM clause is specified by the user.
The proposal is to introduce a parameter with 3 values:
There should be no need to implicitly add LOCK=EXCLUSIVE to each ALTER TABLE statement. That locking mode is rather useless.