Re: Default setting for enable_hashagg_disk

From: Peter Geoghegan <pg(at)bowt(dot)ie>
To: Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>
Cc: Robert Haas <robertmhaas(at)gmail(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Jeff Davis <pgsql(at)j-davis(dot)com>, 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>, Justin Pryzby <pryzby(at)telsasoft(dot)com>, Melanie Plageman <melanieplageman(at)gmail(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Default setting for enable_hashagg_disk
Date: 2020-07-27 15:38:21
Message-ID: CAH2-WznKb9aT2nbUVJnF1qCqYJ+HAj2C2UHe5B_DJqANoAOCmg@mail.gmail.com
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On Sun, Jul 26, 2020 at 11:34 AM Tomas Vondra
<tomas(dot)vondra(at)2ndquadrant(dot)com> wrote:
> That's 1.6GB, if I read it right. Which is more than 200MB ;-)

Sigh. That solves that "mystery": the behavior that my sorted vs
random example exhibited is a known limitation in hash aggs that spill
(and an acceptable one). The memory usage is reported on accurately by
EXPLAIN ANALYZE.

--
Peter Geoghegan

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