Tomas Vondra <tomas.vondra@2ndquadrant.com> wrote:
> OK, so the reason is that when building child paths, we don't keep the
> pathkeys unless it matches the "interesting" pathkeys.
>
> So for example we may have an IndexPath, but with pathkeys=NIL if the
> index does not match the ORDER BY we need.
I don't agree that IndexPath will necessarily have pathkeys set to NIL in such
a case. Even if the index ordering does not match ORDER BY clause of the
query, the path can still be useful, typically for merge join.
--
Antonin Houska
Cybertec Schönig & Schönig GmbH
Gröhrmühlgasse 26, A-2700 Wiener Neustadt
Web: https://www.cybertec-postgresql.com
