Re: postgres_fdw join pushdown (was Re: Custom/Foreign-Join-APIs)

* Is it safe to replace outerjoinpath with its fdw_outerpath the following way?  I think that if the join relation represented by outerjoinpath has local conditions that can't be executed remotely, we have to keep outerjoinpath in the path tree; we will otherwise fail to execute the local conditions.  No?

+                       /*
+                        * If either inner or outer path is a ForeignPath corresponding to
+                        * a pushed down join, replace it with the fdw_outerpath, so that we
+                        * maintain path for EPQ checks built entirely of local join
+                        * strategies.
+                        */
+                       if (IsA(joinpath->outerjoinpath, ForeignPath))
+                       {
+                               ForeignPath *foreign_path;
+                               foreign_path = (ForeignPath *)joinpath->outerjoinpath;
+                               if (foreign_path->path.parent->reloptkind == RELOPT_JOINREL)
+                                       joinpath->outerjoinpath = foreign_path->fdw_outerpath;
+                       }