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

Tom,

* Tom Lane (tgl(at)sss(dot)pgh(dot)pa(dot)us) wrote:
> David Steele <david(at)pgmasters(dot)net> writes:
> > On 3/6/17 12:48 PM, Robert Haas wrote:
> >> 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.
>
> Yes, I think it's rather silly not to do so. We have made comparable
> backpatched fixes multiple times in the past. What is worth discussing is
> whether there are *additional* things we ought to do in 9.6 to prevent
> misbehavior in installations initdb'd pre-9.6.3.
>
> If there's a cheap way of testing "AmInParallelWorker", I'd be in favor of
> adding a quick-n-dirty test and ereport(ERROR) to these functions in the
> 9.6 branch, so that at least you get a clean error and not some weird
> misbehavior. Not sure if there's anything more we can do than that.

That's more-or-less what I was thinking (and suggested to David over IM
a little while ago, actually). I don't know if there's an easy way to
do such a check, but I don't think it would really need to be
particularly cheap, just not overly complex. These code paths are
certainly not ones that need to be high-performance.

Thanks!

Stephen