> Would it make sense to expand this to something like:
>
> Make it possible for rules to return affected tuples?
>
> I come to this because if you use a rule to create an updateable view,
> you never know how many rows the view actually updated.
>
Updatable views can be (maybe) implemented with updatable cursors.
http://archives.postgresql.org/pgsql-hackers/2007-06/msg00335.php
Regards
Pavel Stehule