RE: Big performance slowdown from 11.2 to 13.3

OK. Will do another round of testing.


-----Original Message-----
From: David Rowley <dgrowleyml@gmail.com> 
Sent: Thursday, July 22, 2021 00:44
To: 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
Subject: Re: Big performance slowdown from 11.2 to 13.3

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