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

David Rowley <dgrowleyml(at)gmail(dot)com> writes:
> The reason I didn't go down the route of SETOP_VAR was that it's still
> a hack, it's just making it look a bit more official. I suppose the
> correct way to fix all this and get rid of the varno==0 stuff forever
> is to have a proper top-level RTE for the top-level set operation and
> make it so each child is an OTHER_MEMBER rel at that query level. It
> felt like going a bit too far to do something like that to fix this
> bug, so I didn't explore that further.

Yeah, I think "more RTEs" is the ultimate solution here, but it's
never risen to the top of my to-do list either. I was kind of
thinking about an RTE per set-op child, though. Not sure if one
for the top-level op, or one for an intermediate op, would help;
though it's certainly possible it would.

regards, tom lane