diff --git a/src/backend/nodes/nodeFuncs.c b/src/backend/nodes/nodeFuncs.c
index 1dc873ed255..cbf15aa48d6 100644
--- a/src/backend/nodes/nodeFuncs.c
+++ b/src/backend/nodes/nodeFuncs.c
@@ -745,6 +745,8 @@ expression_returns_set_walker(Node *node, void *context)
 	/* Avoid recursion for some cases that parser checks not to return a set */
 	if (IsA(node, Aggref))
 		return false;
+	if (IsA(node, GroupingFunc))
+		return false;
 	if (IsA(node, WindowFunc))
 		return false;
 
diff --git a/src/backend/optimizer/path/costsize.c b/src/backend/optimizer/path/costsize.c
index 92b5223fee8..4edc859cb57 100644
--- a/src/backend/optimizer/path/costsize.c
+++ b/src/backend/optimizer/path/costsize.c
@@ -4213,6 +4213,12 @@ cost_qual_eval_walker(Node *node, cost_qual_eval_context *context)
 		 */
 		return false;			/* don't recurse into children */
 	}
+	else if (IsA(node, GroupingFunc))
+	{
+		/* Treat this as having cost 1 */
+		context->total.per_tuple += cpu_operator_cost;
+		return false;			/* don't recurse into children */
+	}
 	else if (IsA(node, CoerceViaIO))
 	{
 		CoerceViaIO *iocoerce = (CoerceViaIO *) node;
diff --git a/src/backend/optimizer/plan/subselect.c b/src/backend/optimizer/plan/subselect.c
index 760865a8636..11e29dd1536 100644
--- a/src/backend/optimizer/plan/subselect.c
+++ b/src/backend/optimizer/plan/subselect.c
@@ -357,15 +357,17 @@ build_subplan(PlannerInfo *root, Plan *plan, PlannerInfo *subroot,
 		Node	   *arg = pitem->item;
 
 		/*
-		 * The Var, PlaceHolderVar, or Aggref has already been adjusted to
-		 * have the correct varlevelsup, phlevelsup, or agglevelsup.
+		 * The Var, PlaceHolderVar, Aggref or GroupingFunc has already been
+		 * adjusted to have the correct varlevelsup, phlevelsup, or
+		 * agglevelsup.
 		 *
-		 * If it's a PlaceHolderVar or Aggref, its arguments might contain
-		 * SubLinks, which have not yet been processed (see the comments for
-		 * SS_replace_correlation_vars).  Do that now.
+		 * If it's a PlaceHolderVar, Aggref or GroupingFunc, its arguments
+		 * might contain SubLinks, which have not yet been processed (see the
+		 * comments for SS_replace_correlation_vars).  Do that now.
 		 */
 		if (IsA(arg, PlaceHolderVar) ||
-			IsA(arg, Aggref))
+			IsA(arg, Aggref) ||
+			IsA(arg, GroupingFunc))
 			arg = SS_process_sublinks(root, arg, false);
 
 		splan->parParam = lappend_int(splan->parParam, pitem->paramId);
@@ -1929,10 +1931,11 @@ process_sublinks_mutator(Node *node, process_sublinks_context *context)
 	}
 
 	/*
-	 * Don't recurse into the arguments of an outer PHV or aggregate here. Any
-	 * SubLinks in the arguments have to be dealt with at the outer query
-	 * level; they'll be handled when build_subplan collects the PHV or Aggref
-	 * into the arguments to be passed down to the current subplan.
+	 * Don't recurse into the arguments of an outer PHV, Aggref or
+	 * GroupingFunc here.  Any SubLinks in the arguments have to be dealt with
+	 * at the outer query level; they'll be handled when build_subplan
+	 * collects the PHV, Aggref or GroupingFunc into the arguments to be
+	 * passed down to the current subplan.
 	 */
 	if (IsA(node, PlaceHolderVar))
 	{
@@ -1944,6 +1947,11 @@ process_sublinks_mutator(Node *node, process_sublinks_context *context)
 		if (((Aggref *) node)->agglevelsup > 0)
 			return node;
 	}
+	else if (IsA(node, GroupingFunc))
+	{
+		if (((GroupingFunc *) node)->agglevelsup > 0)
+			return node;
+	}
 
 	/*
 	 * We should never see a SubPlan expression in the input (since this is
@@ -2056,7 +2064,7 @@ SS_identify_outer_params(PlannerInfo *root)
 	outer_params = NULL;
 	for (proot = root->parent_root; proot != NULL; proot = proot->parent_root)
 	{
-		/* Include ordinary Var/PHV/Aggref params */
+		/* Include ordinary Var/PHV/Aggref/GroupingFunc params */
 		foreach(l, proot->plan_params)
 		{
 			PlannerParamItem *pitem = (PlannerParamItem *) lfirst(l);
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 36d7b53c142..92536f0e13f 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -7541,12 +7541,13 @@ get_parameter(Param *param, deparse_context *context)
 		context->varprefix = true;
 
 		/*
-		 * A Param's expansion is typically a Var, Aggref, or upper-level
-		 * Param, which wouldn't need extra parentheses.  Otherwise, insert
-		 * parens to ensure the expression looks atomic.
+		 * A Param's expansion is typically a Var, Aggref, GroupingFunc, or
+		 * upper-level Param, which wouldn't need extra parentheses.
+		 * Otherwise, insert parens to ensure the expression looks atomic.
 		 */
 		need_paren = !(IsA(expr, Var) ||
 					   IsA(expr, Aggref) ||
+					   IsA(expr, GroupingFunc) ||
 					   IsA(expr, Param));
 		if (need_paren)
 			appendStringInfoChar(context->buf, '(');
@@ -7628,6 +7629,7 @@ isSimpleNode(Node *node, Node *parentNode, int prettyFlags)
 		case T_NextValueExpr:
 		case T_NullIfExpr:
 		case T_Aggref:
+		case T_GroupingFunc:
 		case T_WindowFunc:
 		case T_FuncExpr:
 			/* function-like: name(..) or name[..] */
@@ -7744,6 +7746,7 @@ isSimpleNode(Node *node, Node *parentNode, int prettyFlags)
 				case T_XmlExpr: /* own parentheses */
 				case T_NullIfExpr:	/* other separators */
 				case T_Aggref:	/* own parentheses */
+				case T_GroupingFunc:	/* own parentheses */
 				case T_WindowFunc:	/* own parentheses */
 				case T_CaseExpr:	/* other separators */
 					return true;
@@ -7794,6 +7797,7 @@ isSimpleNode(Node *node, Node *parentNode, int prettyFlags)
 				case T_XmlExpr: /* own parentheses */
 				case T_NullIfExpr:	/* other separators */
 				case T_Aggref:	/* own parentheses */
+				case T_GroupingFunc:	/* own parentheses */
 				case T_WindowFunc:	/* own parentheses */
 				case T_CaseExpr:	/* other separators */
 					return true;
diff --git a/src/test/regress/expected/groupingsets.out b/src/test/regress/expected/groupingsets.out
index 7c844c6e09e..1ed034ca06f 100644
--- a/src/test/regress/expected/groupingsets.out
+++ b/src/test/regress/expected/groupingsets.out
@@ -1929,4 +1929,49 @@ set work_mem to default;
 
 drop table gs_group_1;
 drop table gs_hash_1;
+-- test handling of outer GroupingFunc within subqueries
+explain (costs off)
+select (select grouping(v1)) from (values ((select 1))) v(v1) group by cube(v1);
+        QUERY PLAN         
+---------------------------
+ MixedAggregate
+   Hash Key: $2
+   Group Key: ()
+   InitPlan 1 (returns $1)
+     ->  Result
+   InitPlan 3 (returns $2)
+     ->  Result
+   ->  Result
+   SubPlan 2
+     ->  Result
+(10 rows)
+
+select (select grouping(v1)) from (values ((select 1))) v(v1) group by cube(v1);
+ grouping 
+----------
+        1
+        0
+(2 rows)
+
+explain (costs off)
+select (select grouping(v1)) from (values ((select 1))) v(v1) group by v1;
+        QUERY PLAN         
+---------------------------
+ GroupAggregate
+   Group Key: $2
+   InitPlan 1 (returns $1)
+     ->  Result
+   InitPlan 3 (returns $2)
+     ->  Result
+   ->  Result
+   SubPlan 2
+     ->  Result
+(9 rows)
+
+select (select grouping(v1)) from (values ((select 1))) v(v1) group by v1;
+ grouping 
+----------
+        0
+(1 row)
+
 -- end
diff --git a/src/test/regress/sql/groupingsets.sql b/src/test/regress/sql/groupingsets.sql
index 18ae803e9de..d83ca2aa828 100644
--- a/src/test/regress/sql/groupingsets.sql
+++ b/src/test/regress/sql/groupingsets.sql
@@ -529,4 +529,13 @@ set work_mem to default;
 drop table gs_group_1;
 drop table gs_hash_1;
 
+-- test handling of outer GroupingFunc within subqueries
+explain (costs off)
+select (select grouping(v1)) from (values ((select 1))) v(v1) group by cube(v1);
+select (select grouping(v1)) from (values ((select 1))) v(v1) group by cube(v1);
+
+explain (costs off)
+select (select grouping(v1)) from (values ((select 1))) v(v1) group by v1;
+select (select grouping(v1)) from (values ((select 1))) v(v1) group by v1;
+
 -- end