Re: Switching to 64-bit Bitmapsets - Mailing list pgsql-hackers

From Tom Lane
Subject Re: Switching to 64-bit Bitmapsets
Date
Msg-id 22492.1545281424@sss.pgh.pa.us
Whole thread Raw
In response to Switching to 64-bit Bitmapsets  (David Rowley <david.rowley@2ndquadrant.com>)
Responses Re: Switching to 64-bit Bitmapsets  (David Rowley <david.rowley@2ndquadrant.com>)
List pgsql-hackers
David Rowley <david.rowley@2ndquadrant.com> writes:
> I've attached the trivial patch which implements 64-bit Bitmapsets.

> One caveat about this may be that it will likely slow performance for
> 32-bit machines.  My current thinking about that is that such a
> platform is likely not that common a target for the latest version of
> PostgreSQL.

Yeah, I think we've been optimizing for 64-bit platforms for awhile.
I'm not prepared to abandon "it works on 32-bit", but I don't see a
reason to sacrifice 64-bit performance to improve the 32-bit case.

> However, I doubt it would take much more effort to maintain
> using 32-bit sets on 32-bit machines.  If someone feels strongly about
> that then I can adjust the patch to allow that.

Hm, are you thinking of making BITS_PER_BITMAPWORD match sizeof(Pointer)
or something like that?  That seems like a good compromise from here.

            regards, tom lane


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