Horton

Re: Big performance slowdown from 11.2 to 13.3

David Rowley <dgrowleyml@gmail.com>

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From: David Rowley <dgrowleyml@gmail.com>
To: "ldh@laurent-hasson.com" <ldh@laurent-hasson.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, Peter Geoghegan <pg@bowt.ie>, Justin Pryzby <pryzby@telsasoft.com>, "pgsql-performance@postgresql.org" <pgsql-performance@postgresql.org>
Date: 2021-07-22T04:43:51Z
Lists: pgsql-performance 
On Thu, 22 Jul 2021 at 16:37, ldh@laurent-hasson.com
<ldh@laurent-hasson.com> wrote:
> Seems like no cigar ☹ See plan pasted below. I changed the conf as follows:
>   - hash_mem_multiplier = '2'
>   - work_mem = '1GB'

>         Batches: 5  Memory Usage: 2400305kB  Disk Usage: 126560kB

You might want to keep going higher with hash_mem_multiplier until you
see no "Disk Usage" there.  As mentioned, v11 didn't spill to disk and
just used all the memory it pleased.  That was a bit dangerous as it
could result in OOM, so it was fixed.

David

Commits

  1. Get rid of artificial restriction on hash table sizes on Windows.