3 files changed, 49 insertions, 2 deletions

diff --git a/src/backend/optimizer/path/joinpath.c b/src/backend/optimizer/path/joinpath.c
index f047ad9ba46..4b58936fa4c 100644
--- a/src/backend/optimizer/path/joinpath.c
+++ b/src/backend/optimizer/path/joinpath.c
@@ -24,6 +24,7 @@
 #include "optimizer/pathnode.h"
 #include "optimizer/paths.h"
 #include "optimizer/planmain.h"
+#include "optimizer/restrictinfo.h"
 #include "utils/typcache.h"
 
 /* Hook for plugins to get control in add_paths_to_joinrel() */
@@ -130,6 +131,7 @@ add_paths_to_joinrel(PlannerInfo *root,
 {
 	JoinPathExtraData extra;
 	bool		mergejoin_allowed = true;
+	bool		consider_join_pushdown = false;
 	ListCell   *lc;
 	Relids		joinrelids;
 
@@ -322,12 +324,24 @@ add_paths_to_joinrel(PlannerInfo *root,
 							 jointype, &extra);
 
 	/*
+	 * createplan.c does not currently support handling of pseudoconstant
+	 * clauses assigned to joins pushed down by extensions; check if the
+	 * restrictlist has such clauses, and if so, disallow pushing down joins.
+	 */
+	if ((joinrel->fdwroutine &&
+		 joinrel->fdwroutine->GetForeignJoinPaths) ||
+		set_join_pathlist_hook)
+		consider_join_pushdown = !has_pseudoconstant_clauses(root,
+															 restrictlist);
+
+	/*
 	 * 5. If inner and outer relations are foreign tables (or joins) belonging
 	 * to the same server and assigned to the same user to check access
 	 * permissions as, give the FDW a chance to push down joins.
 	 */
 	if (joinrel->fdwroutine &&
-		joinrel->fdwroutine->GetForeignJoinPaths)
+		joinrel->fdwroutine->GetForeignJoinPaths &&
+		consider_join_pushdown)
 		joinrel->fdwroutine->GetForeignJoinPaths(root, joinrel,
 												 outerrel, innerrel,
 												 jointype, &extra);
@@ -335,7 +349,8 @@ add_paths_to_joinrel(PlannerInfo *root,
 	/*
 	 * 6. Finally, give extensions a chance to manipulate the path list.
 	 */
-	if (set_join_pathlist_hook)
+	if (set_join_pathlist_hook &&
+		consider_join_pushdown)
 		set_join_pathlist_hook(root, joinrel, outerrel, innerrel,
 							   jointype, &extra);
 }
diff --git a/src/backend/optimizer/util/restrictinfo.c b/src/backend/optimizer/util/restrictinfo.c
index d6d26a2b515..c1fbbb6bfee 100644
--- a/src/backend/optimizer/util/restrictinfo.c
+++ b/src/backend/optimizer/util/restrictinfo.c
@@ -550,6 +550,36 @@ extract_actual_join_clauses(List *restrictinfo_list,
 }
 
 /*
+ * has_pseudoconstant_clauses
+ *
+ * Returns true if 'restrictinfo_list' includes pseudoconstant clauses.
+ *
+ * This is used when we determine whether to allow extensions to consider
+ * pushing down joins in add_paths_to_joinrel().
+ */
+bool
+has_pseudoconstant_clauses(PlannerInfo *root,
+						   List *restrictinfo_list)
+{
+	ListCell   *l;
+
+	/* No need to look if we know there are no pseudoconstants */
+	if (!root->hasPseudoConstantQuals)
+		return false;
+
+	/* See if there are pseudoconstants in the RestrictInfo list */
+	foreach(l, restrictinfo_list)
+	{
+		RestrictInfo *rinfo = lfirst_node(RestrictInfo, l);
+
+		if (rinfo->pseudoconstant &&
+			!rinfo_is_constant_true(rinfo))
+			return true;
+	}
+	return false;
+}
+
+/*
  * join_clause_is_movable_to
  *		Test whether a join clause is a safe candidate for parameterization
  *		of a scan on the specified base relation.
diff --git a/src/include/optimizer/restrictinfo.h b/src/include/optimizer/restrictinfo.h
index e140e619ace..14cdce750cb 100644
--- a/src/include/optimizer/restrictinfo.h
+++ b/src/include/optimizer/restrictinfo.h
@@ -43,6 +43,8 @@ extern void extract_actual_join_clauses(List *restrictinfo_list,
 										Relids joinrelids,
 										List **joinquals,
 										List **otherquals);
+extern bool has_pseudoconstant_clauses(PlannerInfo *root,
+									   List *restrictinfo_list);
 extern bool join_clause_is_movable_to(RestrictInfo *rinfo, RelOptInfo *baserel);
 extern bool join_clause_is_movable_into(RestrictInfo *rinfo,
 										Relids currentrelids,