Re: Making empty Bitmapsets always be NULL - Mailing list pgsql-hackers

On Tue, Feb 28, 2023 at 1:59 PM Tom Lane <tgl@sss.pgh.pa.us> wrote:
> I also discovered that nodeAppend.c is relying on bms_del_members
> not reducing a non-empty set to NULL, because it uses the nullness
> of appendstate->as_valid_subplans as a state boolean.

I seem to recall that Deep and I tripped into this during the zedstore
column projection work. I think we started out using NULL as a
sentinel value for our bitmaps, too, and it looked like it worked,
until it didn't... so +1 to the simplification.

--Jacob