postgres
diff --git a/‎src/backend/optimizer/plan/planner.c
Lines changed: 2 additions & 1 deletion b/‎src/backend/optimizer/plan/planner.c
Lines changed: 2 additions & 1 deletion
diff --git a/‎src/backend/optimizer/util/pathnode.c
Lines changed: 29 additions & 16 deletions b/‎src/backend/optimizer/util/pathnode.c
Lines changed: 29 additions & 16 deletions
diff --git a/‎src/test/regress/expected/select_parallel.out
Lines changed: 25 additions & 0 deletions b/‎src/test/regress/expected/select_parallel.out
Lines changed: 25 additions & 0 deletions
diff --git a/‎src/test/regress/sql/select_parallel.sql
Lines changed: 13 additions & 0 deletions b/‎src/test/regress/sql/select_parallel.sql
Lines changed: 13 additions & 0 deletions
@@ -5060,7 +5060,8 @@ create_ordered_paths(PlannerInfo *root,
 			path = (Path *)
 				create_gather_merge_path(root, ordered_rel,
 										 path,
-										 target, root->sort_pathkeys, NULL,
+										 path->pathtarget,
+										 root->sort_pathkeys, NULL,
 										 &total_groups);
 
 			/* Add projection step if needed */
 
@@ -2368,9 +2368,9 @@ create_projection_path(PlannerInfo *root,
  * knows that the given path isn't referenced elsewhere and so can be modified
  * in-place.
  *
- * If the input path is a GatherPath, we try to push the new target down to
- * its input as well; this is a yet more invasive modification of the input
- * path, which create_projection_path() can't do.
+ * If the input path is a GatherPath or GatherMergePath, we try to push the
+ * new target down to its input as well; this is a yet more invasive
+ * modification of the input path, which create_projection_path() can't do.
  *
  * Note that we mustn't change the source path's parent link; so when it is
  * add_path'd to "rel" things will be a bit inconsistent.  So far that has
@@ -2407,31 +2407,44 @@ apply_projection_to_path(PlannerInfo *root,
 		(target->cost.per_tuple - oldcost.per_tuple) * path->rows;
 
 	/*
-	 * If the path happens to be a Gather path, we'd like to arrange for the
-	 * subpath to return the required target list so that workers can help
-	 * project.  But if there is something that is not parallel-safe in the
-	 * target expressions, then we can't.
+	 * If the path happens to be a Gather or GatherMerge path, we'd like to
+	 * arrange for the subpath to return the required target list so that
+	 * workers can help project.  But if there is something that is not
+	 * parallel-safe in the target expressions, then we can't.
 	 */
-	if (IsA(path, GatherPath) &&
+	if ((IsA(path, GatherPath) || IsA(path, GatherMergePath)) &&
 		is_parallel_safe(root, (Node *) target->exprs))
 	{
-		GatherPath *gpath = (GatherPath *) path;
-
 		/*
 		 * We always use create_projection_path here, even if the subpath is
 		 * projection-capable, so as to avoid modifying the subpath in place.
 		 * It seems unlikely at present that there could be any other
 		 * references to the subpath, but better safe than sorry.
 		 *
-		 * Note that we don't change the GatherPath's cost estimates; it might
+		 * Note that we don't change the parallel path's cost estimates; it might
 		 * be appropriate to do so, to reflect the fact that the bulk of the
 		 * target evaluation will happen in workers.
 		 */
-		gpath->subpath = (Path *)
-			create_projection_path(root,
-								   gpath->subpath->parent,
-								   gpath->subpath,
-								   target);
+		if (IsA(path, GatherPath))
+		{
+			GatherPath *gpath = (GatherPath *) path;
+
+			gpath->subpath = (Path *)
+				create_projection_path(root,
+									   gpath->subpath->parent,
+									   gpath->subpath,
+									   target);
+		}
+		else
+		{
+			GatherMergePath *gmpath = (GatherMergePath *) path;
+
+			gmpath->subpath = (Path *)
+				create_projection_path(root,
+									   gmpath->subpath->parent,
+									   gmpath->subpath,
+									   target);
+		}
 	}
 	else if (path->parallel_safe &&
 			 !is_parallel_safe(root, (Node *) target->exprs))
 
@@ -375,6 +375,31 @@ select count(*) from tenk1 group by twenty;
    500
 (20 rows)
 
+--test expressions in targetlist are pushed down for gather merge
+create or replace function simple_func(var1 integer) returns integer
+as $$
+begin
+        return var1 + 10;
+end;
+$$ language plpgsql PARALLEL SAFE;
+explain (costs off, verbose)
+    select ten, simple_func(ten) from tenk1 where ten < 100 order by ten;
+                     QUERY PLAN                      
+-----------------------------------------------------
+ Gather Merge
+   Output: ten, (simple_func(ten))
+   Workers Planned: 4
+   ->  Result
+         Output: ten, simple_func(ten)
+         ->  Sort
+               Output: ten
+               Sort Key: tenk1.ten
+               ->  Parallel Seq Scan on public.tenk1
+                     Output: ten
+                     Filter: (tenk1.ten < 100)
+(11 rows)
+
+drop function simple_func(integer);
 --test rescan behavior of gather merge
 set enable_material = false;
 explain (costs off)
 
@@ -144,6 +144,19 @@ explain (costs off)
 
 select count(*) from tenk1 group by twenty;
 
+--test expressions in targetlist are pushed down for gather merge
+create or replace function simple_func(var1 integer) returns integer
+as $$
+begin
+        return var1 + 10;
+end;
+$$ language plpgsql PARALLEL SAFE;
+
+explain (costs off, verbose)
+    select ten, simple_func(ten) from tenk1 where ten < 100 order by ten;
+
+drop function simple_func(integer);
+
 --test rescan behavior of gather merge
 set enable_material = false;