Re: Teaching planner to short-circuit empty UNION/EXCEPT/INTERSECT inputs

On Thu, 2 Oct 2025 at 16:21, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> I'm wondering if it could be shortened a great deal by
> handling left-input-dummy and EXCEPT-ALL-with-right-input-dummy
> but leaving the EXCEPT-with-right-input-dummy case unimproved.

Good idea. Less code and still get to keep the one that did well in
the benchmark. See attached.

I ended up splitting the patch in two. 0001 for UNION only, then 0002
for the INTERSECT and EXCEPT.

David