Re: pgsql: Mark pg_start_backup and pg_stop_backup as parallel-restricted.

On 3/6/17 12:48 PM, Robert Haas wrote:
> Mark pg_start_backup and pg_stop_backup as parallel-restricted.
>
> They depend on backend-private state that will not be synchronized by
> the parallel machinery, so they should not be marked parallel-safe.
> This issue also exists in 9.6, but we obviously can't do anything
> about 9.6 clusters that already exist. Possibly this could be
> back-patched so that future 9.6 clusters would come out OK, or
> possibly we should back-patch some other fix, but that would need more
> discussion.

I think it would be worth back-patching the catalog fix for future 9.6
clusters as a start. Parallelism is off by default in 9.6 so that
mitigates some of the problem.

I don't have any regression tests that cover backups when parallelism is
enabled in 9.6, but I'm willing to do that and see if this is a
realistic issue or not.

--
-David
david(at)pgmasters(dot)net