| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Justin Pryzby <pryzby(at)telsasoft(dot)com> |
| Cc: | Peter Geoghegan <pg(at)bowt(dot)ie>, 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 16:56:53 |
| Message-ID: | 788607.1626973013@sss.pgh.pa.us |
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| Lists: | pgsql-performance |
Justin Pryzby <pryzby(at)telsasoft(dot)com> writes:
> 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.
And more to the point, work_mem*hash_mem_multiplier is *also* limited
to 2GB. We didn't think that through very carefully. The point of
the hash_mem_multiplier feature was to allow hash aggregation to still
consume more than the work_mem limit, but we failed to free it from
this 2GB limit.
You're right though that this is Windows-only; on machines with
64-bit "long" there's less of a problem.
regards, tom lane
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