From: | Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com> |
---|---|
To: | Bruce Momjian <bruce(at)momjian(dot)us> |
Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, David Rowley <dgrowleyml(at)gmail(dot)com>, Jeff Davis <pgsql(at)j-davis(dot)com>, Justin Pryzby <pryzby(at)telsasoft(dot)com>, Melanie Plageman <melanieplageman(at)gmail(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Default setting for enable_hashagg_disk |
Date: | 2020-06-26 14:44:14 |
Message-ID: | 20200626144414.rftlidu34rigiulv@development |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-docs pgsql-hackers |
On Fri, Jun 26, 2020 at 12:02:10AM -0400, Bruce Momjian wrote:
>On Fri, Jun 26, 2020 at 01:53:57AM +0200, Tomas Vondra wrote:
>> I'm not saying it's not beneficial to use different limits for different
>> nodes. Some nodes are less sensitive to the size (e.g. sorting often
>> gets faster with smaller work_mem). But I think we should instead have a
>> per-session limit, and the planner should "distribute" the memory to
>> different nodes. It's a hard problem, of course.
>
>Yeah, I am actually confused why we haven't developed a global memory
>allocation strategy and continue to use per-session work_mem.
>
I think it's pretty hard problem, actually. One of the reasons is that
the costing of a node depends on the amount of memory available to the
node, but as we're building the plan bottom-up, we have no information
about the nodes above us. So we don't know if there are operations that
will need memory, how sensitive they are, etc.
And so far the per-node limit served us pretty well, I think. So I'm not
very confused we don't have the per-session limit yet, TBH.
regards
--
Tomas Vondra http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
From | Date | Subject | |
---|---|---|---|
Next Message | Bruce Momjian | 2020-06-26 16:37:26 | Re: Default setting for enable_hashagg_disk |
Previous Message | Bruce Momjian | 2020-06-26 04:02:10 | Re: Default setting for enable_hashagg_disk |
From | Date | Subject | |
---|---|---|---|
Next Message | Fabrízio de Royes Mello | 2020-06-26 14:55:26 | Re: pg_dump bug for extension owned tables |
Previous Message | Ranier Vilela | 2020-06-26 14:31:18 | Possible NULL dereferencing (src/backend/tcop/pquery.c) |