Andrei Elkin <andrei.elkin@mariadb.com> writes:

Indeed a combination of the engine locking protocol and the slave retry applies correctly to IDEMPOTENT mode.

...

The optimistic parallel replication should work correctly with IDEMPOTENT,

Indeed.

Ok good to know. It's definitely a tricky issue, but apparently no known bugs, at least to the two of us. As you saw, I did have to try a test case to feel confident it works ;-) - Kristian.