Re: Add bms_offset_members() function for bitshifting Bitmapsets

From: David Rowley <dgrowleyml(at)gmail(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Chao Li <li(dot)evan(dot)chao(at)gmail(dot)com>, PostgreSQL Developers <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: Add bms_offset_members() function for bitshifting Bitmapsets
Date: 2026-04-15 02:33:36
Message-ID: CAApHDvp=fhr8ksuGyXkwYPXQpYvJ38YMhHvx6JmdD39cAvNRhw@mail.gmail.com
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On Wed, 15 Apr 2026 at 14:30, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>
> David Rowley <dgrowleyml(at)gmail(dot)com> writes:
> > I'd not considered surprise-prone as an aspect. I understand we have
> > bms_join and bms_union, which do the same thing if you only care about
> > the value of the result and not what happens to the inputs.
>
> Sure, but bms_join is an optional optimization of the far safer
> bms_union operation. It bothers me to create the optimized case
> but not the base case.

Hmm, yeah. That seems like a good argument for making a new set. I'll
go make it so.

David

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