Log Message:
-----------
Teach find_nonnullable_rels to handle OR cases: if every arm of an OR
forces a particular relation nonnullable, then we can say that the OR does.
This is worth a little extra trouble since it may allow reduction of
outer joins to plain joins.
Modified Files:
--------------
pgsql/src/backend/optimizer/util:
clauses.c (r1.233 -> r1.234)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/optimizer/util/clauses.c.diff?r1=1.233&r2=1.234)