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Re: Aliasing slave_parallel_workers/slave_parallel_threads
On 26.01.2016 15:13, Kristian Nielsen wrote:
Colin Charles <byte@xxxxxxxxxxx> writes:
MySQL 5.7 has been released and I’m sure you realise that it uses the
MariaDB Server 10.1 we use slave_parallel_threads
It would be wise for us to alias this, so that its easier from a DBA usability standpoint IMHO
The problem with doing this is that the options are not identical between
MySQL and MariaDB. This means that users/DBAs can experience unpleasant
surprises when their configuration carries over from one to the other but
then silently does the wrong thing.
For example, --slave-parallel-workers in MySQL enables out-of-order parallel
replication between schemas. This can break replication unless applications
are careful to avoid cross-schema queries. In contrast, MariaDB
--slave-parallel-threads is in-order (unless GTID is used), so does not
restrict applications. This means that moving from a MariaDB with
--slave-parallel-workers set to MySQL can silently break replication.
But maybe the options are sufficiently similar (or maybe we do not care
about MariaDB->MySQL migrations). If the consensus is to add the alias, I
do not have a strong opinion one way or the other.
Attached is a patch that implements this. Monty or Sanja, can one of you
review the patch? IIRC, you worked previously on MySQL option compatibility.
The patch is OK, but please run full test suite, IMHO sys_vars shouod
bring some surprises to fix.