Re: Revert: Remove useless self-joins *and* -DREALLOCATE_BITMAPSETS make server crash, regress test fail.

On Wed, 8 May 2024 at 10:40, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>
> David Rowley <dgrowleyml@gmail.com> writes:
> > We could make the policy copy-on-modify.  If you put bms_copy around
> > the bms_del_member() calls in remove_rel_from_query(), does it pass
> > then?
>
> Didn't test, but that route seems awfully invasive and fragile: how
> will we find all the places to modify, or ensure that the policy
> is followed by future patches?

REALLOCATE_BITMAPSETS was invented for this and IMO, it found exactly
the problem it was invented to find.

Copy-on-modify is our policy for node mutation. Why is it ok there but
awfully fragile here?

David