Vik Fearing <vik(at)postgresfriends(dot)org> writes:
> I allowed for this by saying it could be a single group with no rows if
> you preferred to look at it that way.
That is exactly what the standard says.
> This does not explain why the WHERE FALSE is being ignored and producing
> rows.
It's not ignored, but it applies to the pre-grouping rows, of which
there aren't any to remove. But there's still a group.
regards, tom lane