| From: | Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> |
|---|---|
| To: | James Coleman <jtc331(at)gmail(dot)com> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, luis(dot)roberto(at)siscobra(dot)com(dot)br, pgsql-bugs <pgsql-bugs(at)lists(dot)postgresql(dot)org>, "alan(dot)formagi" <alan(dot)formagi(at)siscobra(dot)com(dot)br>, Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com> |
| Subject: | Re: segfault with incremental sort |
| Date: | 2020-11-24 02:27:40 |
| Message-ID: | CAA4eK1K+aWZqgps21_Wa7-HjztUis4XYnPv2HaymNi=rs2yeWg@mail.gmail.com |
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| Lists: | pgsql-bugs |
On Mon, Nov 23, 2020 at 7:12 PM James Coleman <jtc331(at)gmail(dot)com> wrote:
>
> On Tue, Nov 3, 2020 at 1:48 PM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> >
> > James Coleman <jtc331(at)gmail(dot)com> writes:
> > > I also noticed that the incremental sort plan posted earlier has
> > > multiple Gather Merge nodes; that's not what I would have expected,
> > > but maybe I'm missing something.
> >
> > Hm. There is only one Gather Merge in the repro case.
>
> I'm able to reproduce having a gather merge underneath each side of a
> merge right join with a related bugfix patch applied (0001 in [1]).
> But I didn't know if this was a big no-no, or if it's just rare, and
> so a bit unexpected, but not necessarily incorrect.
>
I also think such a plan should be fine and shouldn't result in any error.
> What we _don't_
> have is a gather merge underneath a gather merge, which is what I
> think would definitely be incorrect.
>
Right.
--
With Regards,
Amit Kapila.
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