On Sat, Apr 18, 2026, at 3:49 AM, David Rowley wrote:
> On Wed, 15 Apr 2026 at 14:33, David Rowley <dgrowleyml@gmail.com> wrote:
>>
>> On Wed, 15 Apr 2026 at 14:30, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> >
>> > David Rowley <dgrowleyml@gmail.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.
>
> Patch attached for the version that creates a new set rather than
> modifying the input set in-place.
>
> David
Hey David,
> Attachments:
> * v2-0001-Introduce-bms_offset_members-function.patch
I applied, tested, and reviewed these changes. Thanks for doing this, only a few small things jumped out.
nit: in bitmapset.c there is a new line added above bms_add_range()
+ * Arguments:
+ * arg1: optional random seed, or < 0 to use a random seed.
+ * arg2: the number of operations to perform.
+ * arg3: the maximum bitmapset member number to use in the random set.
+ * arg4: the minimum bitmapset member number to use in the random set.
nit: whitespace ahead of arg1, also should be "NULL" not "< 0"
in test_bitmapset.sql
+-- perform some random test on bms_offset_members()
nit: "tests"
Also, I think the random testing will likely cover these, but here are a few more explicit tests for odd corner cases.
-- shift that shrinks nwords
SELECT test_bms_offset_members('(b 64 65 66)', -64); -- drops into word 0
-- shift that drops some low members and keeps others
SELECT test_bms_offset_members('(b 0 1 2 10)', -2); -- expect (b 0 8)
-- entire set shifts below zero -> empty
SELECT test_bms_offset_members('(b 1 2 3)', -10); -- expect empty
-- word-aligned positive and negative shifts
SELECT test_bms_offset_members('(b 1 2 3)', 64);
SELECT test_bms_offset_members('(b 65 66 67)', -64);
-- INT_MIN boundary
SELECT test_bms_offset_members('(b 1)', -2147483648);
I like the functionality and the reduction of repeated code that you've identified and fixed.
best.
-greg
