Re: BUG #15669: Error with unnest in PG 11 (ERROR: 0A000)

On Tue, Mar 5, 2019 at 5:34 PM Julien Rouhaud <rjuju123@gmail.com> wrote:
>
> On Tue, Mar 5, 2019 at 4:39 PM Tom Lane <tgl@sss.pgh.pa.us> wrote:
> >
> > PG Bug reporting form <noreply@postgresql.org> writes:
> > > In PostgreSQL 10.7 and before, it is possible to run the following query:
> >
> > > thibaut=# WITH test AS ( SELECT array[1,2] AS intarr )
> > >                  SELECT unnest(intarr) AS lot_id FROM test WHERE false;
> >
> > > In version 11.2, the same query fails:
> > > ERROR:  0A000: set-valued function called in context that cannot accept a set
> >
> > Hmm, that's definitely a bug.  It looks like we're forgetting to make
> > a ProjectSet plan node for the unnest() if we realize that the query
> > is a no-op; but I'm not sure why 10.x doesn't have the same issue.
> > Digging ...
>
> It seems to be due to 11cf92f6e2e which bypass adjust_paths_for_srfs()
> in case of dummy rel.  I'm not familiar with that this code, but
> attached patch seems to fix the issue without breaking regression
> tests.

I forgot to add a regression test, fixed in v2 with a simplified test case.