On Sun, 2015-05-03 at 13:00 -0400, Tom Lane wrote:
> I don't think there's any useful alternative to failing on this type of
> case. You can't realistically postpone resolution of the subquery output
> types long enough for outer-level expression resolution to provide
> context. Even if you could, the behavior wouldn't be very well defined,
> because (as you note) there might be more than one such expression leading
> to contradictory results.
>
> I think it's reasonable to try to let context inform resolution of the
> subquery output types where there is exactly one immediate source of
> context, such as the INSERT/SELECT case or UNION/INTERSECT/EXCEPT cases.
> (Upthread, Kevin whines about our handling of UNION, but that's possibly
> fixable.)
OK, your proposal sounds good to me then.
Regards,
Jeff Davis