From: Tom Lane <tgl@sss.pgh.pa.us>
To: David Rowley <david.rowley@2ndquadrant.com>
cc: Jesper Pedersen <jesper.pedersen@redhat.com>,
        Andres Freund <andres@anarazel.de>,
        Robert Haas <robertmhaas@gmail.com>,
        PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Subject: Re: POC: converting Lists into arrays
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Comments: In-reply-to David Rowley <david.rowley@2ndquadrant.com>
	message dated "Mon, 22 Jul 2019 16:46:02 +1200"
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Date: Mon, 22 Jul 2019 00:54:00 -0400
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David Rowley <david.rowley@2ndquadrant.com> writes:
> On Mon, 22 Jul 2019 at 16:37, Tom Lane <tgl@sss.pgh.pa.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