On 2/9/18 09:42, Tom Lane wrote:
> Meh. It doesn't look significantly different to me than the restriction
> that you can't have sub-selects in CHECK expressions, index expressions,
> etc. Obviously we need a clean failure like you get for those cases.
> But otherwise it's an OK restriction that stems from exactly the same
> cause: we do not want to invoke the full planner in this context (and
> even if we did, we don't want to use the full executor to execute the
> result).
A close analogy is that EXECUTE parameters also don't accept subqueries.
It would perhaps be nice if that could be made to work, but as
discussed it would require a bunch more work.
--
Peter Eisentraut http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services