Re: Big performance slowdown from 11.2 to 13.3

From: Justin Pryzby <pryzby(at)telsasoft(dot)com>
To: Peter Geoghegan <pg(at)bowt(dot)ie>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, David Rowley <dgrowleyml(at)gmail(dot)com>, "ldh(at)laurent-hasson(dot)com" <ldh(at)laurent-hasson(dot)com>, "pgsql-performance(at)postgresql(dot)org" <pgsql-performance(at)postgresql(dot)org>
Subject: Re: Big performance slowdown from 11.2 to 13.3
Date: 2021-07-22 16:41:27
Message-ID: 20210722164127.GI19620@telsasoft.com
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On Thu, Jul 22, 2021 at 09:36:02AM -0700, Peter Geoghegan wrote:
> I don't see how it's possible for get_hash_mem() to be unable to
> return a hash_mem value that could be represented by work_mem
> directly. MAX_KILOBYTES is an annoyingly low limit on Windows, where
> sizeof(long) is 4. But that's nothing new.

Oh. So the problem seems to be that:

1) In v12, HashAgg now obeyes work_mem*hash_mem_multiplier;
2) Under windows, work_mem is limited to 2GB.

--
Justin

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