Re: pgsql: Handle lack of DSM slots in parallel btree build.

Hi Peter,

On Tue, Feb 4, 2020 at 9:13 AM Peter Geoghegan <pg@bowt.ie> wrote:
> On Thu, Jan 30, 2020 at 2:34 PM Thomas Munro <tmunro@postgresql.org> wrote:
> > Handle lack of DSM slots in parallel btree build.
> >
> > If no DSM slots are available, a ParallelContext can still be
> > created, but its seg pointer is NULL.  Teach parallel btree build
> > to cope with that by falling back to a regular non-parallel build,
> > to avoid crashing with a segmentation fault.
>
> Uh, this seems to have completely disabled parallel index builds on
> the master branch.

Oops.  The check needs to move down below InitializeParallelDSM(), and
release any extra resources that might have been acquired (snapshot?).
I will do some testing in a few hours and post a fix.