| From: | David Rowley <dgrowleyml(at)gmail(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Jeff Janes <jeff(dot)janes(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: Bitmap reuse |
| Date: | 2021-07-21 13:58:29 |
| Message-ID: | CAApHDvptE7BERTdygz78NdH-s6Ztbov6-iUgyzhhWOzj33M7hA@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Thu, 22 Jul 2021 at 01:54, David Rowley <dgrowleyml(at)gmail(dot)com> wrote:
> Maybe the planner would need to be involved in making the decision of
> if the bitmap index scan should tuck away a carbon copy of the
> resulting TIDBitmap after the first scan. That way on rescan we could
> just make a copy of the cached version and return that. That saves
> having to modify the callers to tell them not to damage the returned
> TIDBitmap.
Oh but, meh. Caching could blow out work_mem... We might end up using
work_mem * 2.
David
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