| From: | Peter Geoghegan <pg(at)bowt(dot)ie> |
|---|---|
| To: | Jeff Davis <pgsql(at)j-davis(dot)com> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, David Rowley <dgrowleyml(at)gmail(dot)com>, Stephen Frost <sfrost(at)snowman(dot)net>, Andres Freund <andres(at)anarazel(dot)de>, Bruce Momjian <bruce(at)momjian(dot)us>, Robert Haas <robertmhaas(at)gmail(dot)com>, Justin Pryzby <pryzby(at)telsasoft(dot)com>, Melanie Plageman <melanieplageman(at)gmail(dot)com>, Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Default setting for enable_hashagg_disk |
| Date: | 2020-07-19 21:23:11 |
| Message-ID: | CAH2-WzmaQ3Z5So5=MieG4Vzoa2wLuKiXUcAOsJ_eMNdsZi=A7g@mail.gmail.com |
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On Sat, Jul 18, 2020 at 3:04 PM Jeff Davis <pgsql(at)j-davis(dot)com> wrote:
> > I think the entire discussion
> > is way out ahead of any field evidence that we need such a knob.
> > In the absence of evidence, our default position ought to be to
> > keep it simple, not to accumulate backwards-compatibility kluges.
>
> Fair enough. I think that was where Stephen and Amit were coming from,
> as well.
> That would lessen the number of changed plans, but we could easily
> remove the pessimization without controversy later if it turned out to
> be unnecessary, or if we further optimize HashAgg IO.
Does this mean that we've reached a final conclusion on
hashagg_avoid_disk_plan for Postgres 13, which is that it should be
removed? If so, I'd appreciate it if you took care of it. I don't
think that we need to delay its removal until the details of the
HashAgg cost pessimization are finalized. (I expect that that will be
totally uncontroversial.)
Thanks
--
Peter Geoghegan
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