Re: hashagg slowdown due to spill changes

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, Jeff Davis <pgsql(at)j-davis(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, Tomas Vondra <tv(at)fuzzy(dot)cz>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org>, Melanie Plageman <melanieplageman(at)gmail(dot)com>
Subject: Re: hashagg slowdown due to spill changes
Date: 2020-06-15 16:46:33
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Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> On Mon, Jun 15, 2020 at 9:34 AM Tomas Vondra
> <tomas(dot)vondra(at)2ndquadrant(dot)com> wrote:
>> But just reverting 4cad2534d will make this much worse, I think, as
>> illustrated by the benchmarks I did in [1].

> I share this concern, although I do not know what we should do about it.

Well, it's only June. Let's put it on the open issues list for v13
and continue to think about it. I concur that the hashagg spill patch
has made this something that we should worry about for v13, so just
reverting without a better answer isn't very appetizing.

regards, tom lane

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