RE: Big performance slowdown from 11.2 to 13.3

OK. Will do another round of testing.

-----Original Message-----
From: David Rowley <dgrowleyml(at)gmail(dot)com>
Sent: Thursday, July 22, 2021 00:44
To: ldh(at)laurent-hasson(dot)com
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>; Peter Geoghegan <pg(at)bowt(dot)ie>; Justin Pryzby <pryzby(at)telsasoft(dot)com>; pgsql-performance(at)postgresql(dot)org
Subject: Re: Big performance slowdown from 11.2 to 13.3

On Thu, 22 Jul 2021 at 16:37, ldh(at)laurent-hasson(dot)com <ldh(at)laurent-hasson(dot)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