Re: parallel explain analyze support not exercised

On 2017-04-03 15:13:13 -0400, Robert Haas wrote:
> On Mon, Apr 3, 2017 at 1:53 PM, Andres Freund <andres@anarazel.de> wrote:
> >> Please find the attached for the same.
> >
> >> +-- to increase the parallel query test coverage
> >> +EXPLAIN (analyze, timing off, summary off, costs off) SELECT * FROM tenk1;
> >> +                         QUERY PLAN
> >> +-------------------------------------------------------------
> >> + Gather (actual rows=10000 loops=1)
> >> +   Workers Planned: 4
> >> +   Workers Launched: 4
> >> +   ->  Parallel Seq Scan on tenk1 (actual rows=2000 loops=5)
> >> +(4 rows)
> >
> > Is there an issue that we might not actually be able to start all four
> > workers?  Serious question, not rhetorical.
> 
> If this is 'make check', then we should have 8 parallel workers
> allowed, so if we only do one of these at a time, then I think we're
> OK.  But if somebody changes that configuration setting or if it's
> 'make installcheck', then the configuration could be anything.

Hm - we already rely on max_parallel_workers_per_gather being set with
some of the explains in the test.  So I guess we're ok also relying on
actual workers being present?

- Andres