| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | David Rowley <david(dot)rowley(at)2ndquadrant(dot)com> |
| Cc: | Jesper Pedersen <jesper(dot)pedersen(at)redhat(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, Robert Haas <robertmhaas(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: POC: converting Lists into arrays |
| Date: | 2019-07-22 04:54:00 |
| Message-ID: | 29776.1563771240@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
David Rowley <david(dot)rowley(at)2ndquadrant(dot)com> writes:
> On Mon, 22 Jul 2019 at 16:37, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> Interesting. I wonder if bms_next_member() could be made any quicker?
> I had a quick look earlier and the only thing I saw was maybe to do
> the first loop differently from subsequent ones. The "w &= mask;"
> does nothing useful once we're past the first bitmapword that the loop
> touches.
Good thought, but it would only help when we're actually iterating to
later words, which happens just 1 out of 64 times in the fully-
populated-bitmap case.
Still, I think it might be worth pursuing to make the sparse-bitmap
case faster.
regards, tom lane
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