Feedback-ID: i675e48f3:Fastmail
MIME-Version: 1.0
Date: Mon, 20 Apr 2026 10:55:09 -0400
From: "Greg Burd" <greg@burd.me>
To: "David Rowley" <dgrowleyml@gmail.com>
Cc: "Tom Lane" <tgl@sss.pgh.pa.us>, "Chao Li" <li.evan.chao@gmail.com>,
 "PostgreSQL Hackers" <pgsql-hackers@lists.postgresql.org>
Message-Id: <6cb75f47-261b-4476-b8e8-18fa6aad464f@app.fastmail.com>
In-Reply-To: 
 <CAApHDvqOgtX2MqaPmPmPET7=ySszzuoP3MLSUbWZit_V30VBLg@mail.gmail.com>
References: 
 <CAApHDvq=eEdw2Qp+aSzSOtTSe+h0fnVQ55CcTNqBkLDYiRZmxw@mail.gmail.com>
 <278B9FE3-F349-4494-99C5-483105C1C999@gmail.com>
 <CAApHDvoALVPgVSCuGdAfNUbxx_NacnAd0nuj8Hi=_-61AEqzaQ@mail.gmail.com>
 <1900289.1776212948@sss.pgh.pa.us>
 <CAApHDvq4_WDfTaWX6nHU8TV+no+aD1zjLphza685Ek7=xgGzew@mail.gmail.com>
 <1913188.1776220247@sss.pgh.pa.us>
 <CAApHDvp=fhr8ksuGyXkwYPXQpYvJ38YMhHvx6JmdD39cAvNRhw@mail.gmail.com>
 <CAApHDvrp6JwOVH3VwMB=YL3p97F5_0hKJc7J8zHRKuyhKru1dA@mail.gmail.com>
 <77f5109f-6d39-4cf1-8d0d-f826435d6cb6@app.fastmail.com>
 <CAApHDvqOgtX2MqaPmPmPET7=ySszzuoP3MLSUbWZit_V30VBLg@mail.gmail.com>
Subject: Re: Add bms_offset_members() function for bitshifting Bitmapsets
Content-Type: text/plain
Content-Transfer-Encoding: 7bit
Archived-At: 
 <https://www.postgresql.org/message-id/6cb75f47-261b-4476-b8e8-18fa6aad464f%40app.fastmail.com>
Precedence: bulk


On Sun, Apr 19, 2026, at 7:52 PM, David Rowley wrote:
> On Mon, 20 Apr 2026 at 07:22, Greg Burd <greg@burd.me> wrote:
>> I applied, tested, and reviewed these changes.  Thanks for doing this, only a few small things jumped out.
>
> Many thanks. I took all of those suggestions.

Happy to help.

>> SELECT test_bms_offset_members('(b 1)', -2147483648);
>
> I made that one use member 0 instead of 1.  That'll mean "new_highest"
> goes to INT_MIN rather than INT_MIN + 1.

Perfect, that covers the gap nicely.

Were you planning on writing the optimized non-copy version as well?  I don't think it is strictly necessary, more a curiosity.

bms_offset_members() -> new bms, might repalloc() replaces existing loops you've found
bms_shift_members() -> bms is modified in place and fits your new use case a bit better

best.

-greg


> David
>
> Attachments:
> * v3-0001-Introduce-bms_offset_members-function.patch