On Thursday, December 21, 2017, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> which would only be the right plan for UNION ALL.
>
> So yeah, it's wrong ... but personally I'm not terribly excited
> about fixing it. Maybe somebody else wants to; but what's the
> practical use?
>
How about just erroring out?
David J.