| From: | Bruce Momjian <bruce(at)momjian(dot)us> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, Tomas Vondra <tomas(dot)vondra(at)enterprisedb(dot)com>, Stephen Frost <sfrost(at)snowman(dot)net>, Oleksii Kliukin <alexk(at)hintbits(dot)com>, Álvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>, Jan Wieck <jan(at)wi3ck(dot)info>, Postgres hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: Limiting memory allocation |
| Date: | 2022-05-25 01:35:19 |
| Message-ID: | Yo2H14iyZ7YmJHra@momjian.us |
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| Lists: | pgsql-hackers |
On Tue, May 24, 2022 at 09:20:43PM -0400, Tom Lane wrote:
> Bruce Momjian <bruce(at)momjian(dot)us> writes:
> > On Tue, May 24, 2022 at 07:40:45PM -0400, Tom Lane wrote:
> >> (1) There are not a predetermined number of allocations. For example,
> >> if we do a given join as nestloop+inner index scan, that doesn't require
> >> any large amount of memory; but if we do it as merge or hash join then
> >> it will consume memory.
>
> > Uh, we know from the plan whether we are doing a nestloop+inner or merge
> > or hash join, right? I was suggesting we look at the plan before
> > execution and set the proper percentage of work_mem for each node.
>
> Then you just rendered all the planner's estimates fantasies.
That's what I was asking --- if the planner's estimates are based on the
size of work_mem --- I thought you said it is not.
--
Bruce Momjian <bruce(at)momjian(dot)us> https://momjian.us
EDB https://enterprisedb.com
Indecision is a decision. Inaction is an action. Mark Batterson
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