Re: POC: converting Lists into arrays - Mailing list pgsql-hackers

From Tom Lane
Subject Re: POC: converting Lists into arrays
Date
Msg-id 29776.1563771240@sss.pgh.pa.us
Whole thread Raw
In response to Re: POC: converting Lists into arrays  (David Rowley <david.rowley@2ndquadrant.com>)
List pgsql-hackers
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



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