| From: | Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Jeff Davis <pgsql(at)j-davis(dot)com>, Peter Geoghegan <pg(at)bowt(dot)ie>, 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>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Default setting for enable_hashagg_disk |
| Date: | 2020-07-20 17:25:39 |
| Message-ID: | 20200720172539.6jov6ynljly4wj6i@development |
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| Lists: | pgsql-docs pgsql-hackers |
On Mon, Jul 20, 2020 at 09:17:21AM -0400, Tom Lane wrote:
>Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com> writes:
>> There's a minor problem here, though - these stats were collected before
>> we fixed the tlist issue, so hashagg was spilling about 10x the amount
>> of data compared to sort+groupagg. So maybe that's the first thing we
>> should do, before contemplating changes to the costing - collecting
>> fresh data. I can do that, if needed.
>
>+1. I'm not sure if we still need to do anything, but we definitely
>can't tell on the basis of data that doesn't reliably reflect what
>the code does now.
>
OK, will do. The hardware is busy doing something else at the moment,
but I'll do the tests and report results in a couple days.
regards
--
Tomas Vondra http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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