| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | David Rowley <dgrowleyml(at)gmail(dot)com> |
| Cc: | "ldh(at)laurent-hasson(dot)com" <ldh(at)laurent-hasson(dot)com>, Peter Geoghegan <pg(at)bowt(dot)ie>, Justin Pryzby <pryzby(at)telsasoft(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 16:21:38 |
| Message-ID: | 786600.1626970898@sss.pgh.pa.us |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-performance |
David Rowley <dgrowleyml(at)gmail(dot)com> writes:
> On Fri, 23 Jul 2021 at 03:56, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> So basically, we now have a hard restriction that hashaggs can't use
>> more than INT_MAX kilobytes, or approximately 2.5GB, and this use case
>> is getting eaten alive by that restriction. Seems like we need to
>> do something about that.
> Hmm, math check?
Yeah, I should have said "2GB plus palloc slop". It doesn't surprise
me a bit that we seem to be eating another 20% on top of the nominal
limit.
I think the right fix here is to remove the cap, which will require
changing get_hash_mem to return double, and then maybe some cascading
changes --- I've not looked at its callers.
regards, tom lane
| From | Date | Subject | |
|---|---|---|---|
| Next Message | Justin Pryzby | 2021-07-22 16:22:54 | Re: Big performance slowdown from 11.2 to 13.3 |
| Previous Message | ldh@laurent-hasson.com | 2021-07-22 16:18:55 | RE: Big performance slowdown from 11.2 to 13.3 |