Re: Proposal: "query_work_mem" GUC, to distribute working memory to the query's individual operators

On Tue, Feb 11, 2025 at 2:04 PM Jeff Davis <pgsql(at)j-davis(dot)com> wrote:
>
...
> Storing work_mem in each Plan node, and using that to enforce the
> memory limit (rather than using the GUC directly), seems
> uncontroversial to me. I'd suggest a standalone patch.

I will submit a patch for this, thanks. (This will be "Patch 3".)

> Storing the optimizer's estimate of the memory wanted also sounds like
> a good idea. Let's pick a better name than "nbytes" though; maybe
> "requested_mem" or something? This change would make it a lot easier
> for an extension to adjust the per-node-work_mem, and also seems like
> good infrastructure for anything we build into the planner later. I
> suggest a standalone patch for this, as well.

I will submit a patch for this as well. (This will be "Patch 1".) I
went with "workmem" instead of "nbytes," for the estimate; and
"workmem_limit" for the limit. By omitting the underscore character
between "work" and "mem", this makes it a bit easier to distinguish
between the "work_mem" GUC, the "workmem" estimate, and the
"workmem_limit" limit.

> Can you write a useful extension with just the above two core patches?

I think so; I will attach a patch for that as well.. (This will be
"Patch 4"; note that "Patch 2" is a prerequisite for "Patch 3".)

> Regards,
> Jeff Davis

Thanks,
James Hunter