Re: Properly pathify the union planner

On Mon, Mar 25, 2024 at 9:44 AM David Rowley <dgrowleyml(at)gmail(dot)com> wrote:

> It seems ok that
> the ec_indexes are not set for the top-level set RelOptInfo as
> get_eclass_for_sort_expr() does not make use of ec_indexes while
> searching for an existing EquivalenceClass. Maybe we should fix this
> varno == 0 hack and adjust get_eclass_for_sort_expr() so that it makes
> use of the ec_indexes.
>
> It's possible to see this happen with a query such as:
>
> SELECT oid FROM pg_class UNION SELECT oid FROM pg_class ORDER BY oid;

I see what you said. Yeah, there might be some optimization
possibilities in this area. And I agree that this should not be a
blocker in pushing this patch.

> I didn't see that as a reason not to push this patch as this occurs
> both with and without this change, so I've now pushed this patch.

Great to see this patch has been pushed!

Thanks
Richard