Fix Memoize to work with partitionwise joining.

A couple of places weren't up to speed for this.  By sheer good
luck, we didn't fail but just selected a non-memoized join plan,
at least in the test case we have.  Nonetheless, it's a bug,
and I'm not quite sure that it couldn't have worse consequences
in other examples.  So back-patch to v14 where Memoize came in.

Richard Guo

Discussion: https://postgr.es/m/CAMbWs48GkNom272sfp0-WeD6_0HSR19BJ4H1c9ZKSfbVnJsvRg@mail.gmail.com

src/backend/optimizer/path/joinpath.c

@@ -505,6 +505,7 @@ get_memoize_path(PlannerInfo *root, RelOptInfo *innerrel,
 				 Path *outer_path, JoinType jointype,
 				 JoinPathExtraData *extra)
 {
+	RelOptInfo *top_outerrel;
 	List	   *param_exprs;
 	List	   *hash_operators;
 	ListCell   *lc;
@@ -594,10 +595,21 @@ get_memoize_path(PlannerInfo *root, RelOptInfo *innerrel,
 			return NULL;
 	}
 
+	/*
+	 * When considering a partitionwise join, we have clauses that reference
+	 * the outerrel's top parent not outerrel itself.
+	 */
+	if (outerrel->reloptkind == RELOPT_OTHER_MEMBER_REL)
+		top_outerrel = find_base_rel(root, bms_singleton_member(outerrel->top_parent_relids));
+	else if (outerrel->reloptkind == RELOPT_OTHER_JOINREL)
+		top_outerrel = find_join_rel(root, outerrel->top_parent_relids);
+	else
+		top_outerrel = outerrel;
+
 	/* Check if we have hash ops for each parameter to the path */
 	if (paraminfo_get_equal_hashops(root,
 									inner_path->param_info,
-									outerrel,
+									top_outerrel,
 									innerrel,
 									&param_exprs,
 									&hash_operators,

src/backend/optimizer/util/pathnode.c

@@ -4193,6 +4193,7 @@ do { \
 
 				FLAT_COPY_PATH(mpath, path, MemoizePath);
 				REPARAMETERIZE_CHILD_PATH(mpath->subpath);
+				ADJUST_CHILD_ATTRS(mpath->param_exprs);
 				new_path = (Path *) mpath;
 			}
 			break;