Kristian, Sergey, hello!
> Sergey Petrunia <ser...@mariadb.com> writes:
>
>> == Symptoms ==
>> When one runs a parallel slave (mode=conservative) and replicates DML for
> Nice analysis. Normally it is guaranteed to be safe to start the next
> transaction in parallel with the commit step of a prior. But as you
> describe, RBR on table with no primary key is special, since it does not
> really correspond to any SQL-level operation.
>
>> 2. Change parallel slave to wait *for commit*. This should only be done if
>> tables that are updated do not support Gap Locking. This is hard, it will
>> require making risky changes on the SQL layer.
>
> I think you can just call thd->wait_for_prior_commit() in the code that does
> the RBR table scan on a table with no primary key. Eg.
> Rows_log_event::find_row():
>
> if (m_key_info)
> {
> ...
> }
> else
> {
> DBUG_PRINT("info",("locating record using table scan (rnd_next)"));
> thd->wait_for_prior_commit();
> ...
> }
>
> (Or do it only once, maybe in Rows_log_event::find_key() or similar, and
> only if rli->mi->parallel_mode==SLAVE_PARALLEL_CONSERVATIVE).
Right, without the if the OPTIMISTIC could not be called such :-).
To me it's the best feasible solution, consistent with the name.
Andrei
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