fix-empty-plan-with-RETURNING-3.patch

diff --git a/src/backend/optimizer/plan/planner.c b/src/backend/optimizer/plan/planner.c
index 5579dfa65e..4a9b9c16f0 100644
--- a/src/backend/optimizer/plan/planner.c
+++ b/src/backend/optimizer/plan/planner.c
@@ -1584,13 +1584,36 @@ inheritance_planner(PlannerInfo *root)
 	 */
 
 	/*
-	 * If we managed to exclude every child rel, return a dummy plan; it
-	 * doesn't even need a ModifyTable node.
+	 * We managed to exclude every child rel, so generate a dummy path
+	 * representing empty set.  Although it's clear that no data will be
+	 * updated or deleted, we will still need to have a ModifyTable node so
+	 * that any statement triggers are executed.
 	 */
 	if (subpaths == NIL)
 	{
-		set_dummy_rel_pathlist(final_rel);
-		return;
+		Path   *dummy_path;
+		List   *tlist;
+
+		tlist = root->processed_tlist = preprocess_targetlist(root);
+		final_rel->reltarget = create_pathtarget(root, tlist);
+
+		/*
+		 * Following information will be needed to make a minimally valid
+		 * ModifyTable.
+		 */
+		dummy_path = (Path *) create_append_path(NULL, final_rel, NIL, NIL,
+												 NULL, 0, false, NIL, -1);
+		resultRelations = list_make1_int(parse->resultRelation);
+		subpaths = list_make1(dummy_path);
+		subroots = list_make1(root);
+		if (parse->returningList)
+			returningLists = list_make1(parse->returningList);
+
+		/*
+		 * At least simple_rte_array must be valid for plan creation to work
+		 * correctly.
+		 */
+		final_rtable = parse->rtable;
 	}
 
 	/*
diff --git a/src/test/regress/expected/inherit.out b/src/test/regress/expected/inherit.out
index f259d07535..565d947b6d 100644
--- a/src/test/regress/expected/inherit.out
+++ b/src/test/regress/expected/inherit.out
@@ -539,6 +539,47 @@ CREATE TEMP TABLE z (b TEXT, PRIMARY KEY(aa, b)) inherits (a);
 INSERT INTO z VALUES (NULL, 'text'); -- should fail
 ERROR:  null value in column "aa" violates not-null constraint
 DETAIL:  Failing row contains (null, text).
+-- Check inherited UPDATE with all children excluded
+create table some_tab (a int, b int);
+create table some_tab_child () inherits (some_tab);
+insert into some_tab_child values(1,2);
+explain (verbose, costs off)
+update some_tab set a = a + 1 where false;
+            QUERY PLAN            
+----------------------------------
+ Update on public.some_tab
+   Update on public.some_tab
+   ->  Result
+         Output: (a + 1), b, ctid
+         One-Time Filter: false
+(5 rows)
+
+update some_tab set a = a + 1 where false;
+explain (verbose, costs off)
+update some_tab set a = a + 1 where false returning b, a;
+            QUERY PLAN            
+----------------------------------
+ Update on public.some_tab
+   Output: b, a
+   Update on public.some_tab
+   ->  Result
+         Output: (a + 1), b, ctid
+         One-Time Filter: false
+(6 rows)
+
+update some_tab set a = a + 1 where false returning b, a;
+ b | a 
+---+---
+(0 rows)
+
+table some_tab;
+ a | b 
+---+---
+ 1 | 2
+(1 row)
+
+drop table some_tab cascade;
+NOTICE:  drop cascades to table some_tab_child
 -- Check UPDATE with inherited target and an inherited source table
 create temp table foo(f1 int, f2 int);
 create temp table foo2(f3 int) inherits (foo);
diff --git a/src/test/regress/expected/triggers.out b/src/test/regress/expected/triggers.out
index 2b908ceec4..40aa8d18ae 100644
--- a/src/test/regress/expected/triggers.out
+++ b/src/test/regress/expected/triggers.out
@@ -2790,3 +2790,35 @@ drop table self_ref;
 drop function dump_insert();
 drop function dump_update();
 drop function dump_delete();
+-- Check that statement triggers work correctly even with an empty update
+create table stmt_trig_on_empty_upd (a int);
+create table stmt_trig_on_empty_upd1 () inherits (stmt_trig_on_empty_upd);
+create or replace function update_stmt_notice() returns trigger as $$
+begin
+	raise notice 'updating %', TG_TABLE_NAME;
+	return null;
+end;
+$$ language plpgsql;
+create trigger before_stmt_trigger
+	before update on stmt_trig_on_empty_upd
+	execute function update_stmt_notice();
+create trigger before_stmt_trigger
+	before update on stmt_trig_on_empty_upd1
+	execute function update_stmt_notice();
+-- inherited update
+update stmt_trig_on_empty_upd set a = a where false returning a+1 as aa;
+NOTICE:  updating stmt_trig_on_empty_upd
+ aa 
+----
+(0 rows)
+
+-- simple update
+update stmt_trig_on_empty_upd1 set a = a where false returning a+1 as aa;
+NOTICE:  updating stmt_trig_on_empty_upd1
+ aa 
+----
+(0 rows)
+
+drop table stmt_trig_on_empty_upd cascade;
+NOTICE:  drop cascades to table stmt_trig_on_empty_upd1
+drop function update_stmt_notice;
diff --git a/src/test/regress/sql/inherit.sql b/src/test/regress/sql/inherit.sql
index 425052c1f4..5480fe7db4 100644
--- a/src/test/regress/sql/inherit.sql
+++ b/src/test/regress/sql/inherit.sql
@@ -97,6 +97,21 @@ SELECT relname, d.* FROM ONLY d, pg_class where d.tableoid = pg_class.oid;
 CREATE TEMP TABLE z (b TEXT, PRIMARY KEY(aa, b)) inherits (a);
 INSERT INTO z VALUES (NULL, 'text'); -- should fail
 
+-- Check inherited UPDATE with all children excluded
+create table some_tab (a int, b int);
+create table some_tab_child () inherits (some_tab);
+insert into some_tab_child values(1,2);
+
+explain (verbose, costs off)
+update some_tab set a = a + 1 where false;
+update some_tab set a = a + 1 where false;
+explain (verbose, costs off)
+update some_tab set a = a + 1 where false returning b, a;
+update some_tab set a = a + 1 where false returning b, a;
+table some_tab;
+
+drop table some_tab cascade;
+
 -- Check UPDATE with inherited target and an inherited source table
 create temp table foo(f1 int, f2 int);
 create temp table foo2(f3 int) inherits (foo);
diff --git a/src/test/regress/sql/triggers.sql b/src/test/regress/sql/triggers.sql
index 60d1dc6f46..73128a6542 100644
--- a/src/test/regress/sql/triggers.sql
+++ b/src/test/regress/sql/triggers.sql
@@ -2124,3 +2124,25 @@ drop table self_ref;
 drop function dump_insert();
 drop function dump_update();
 drop function dump_delete();
+
+-- Check that statement triggers work correctly even with an empty update
+create table stmt_trig_on_empty_upd (a int);
+create table stmt_trig_on_empty_upd1 () inherits (stmt_trig_on_empty_upd);
+create or replace function update_stmt_notice() returns trigger as $$
+begin
+	raise notice 'updating %', TG_TABLE_NAME;
+	return null;
+end;
+$$ language plpgsql;
+create trigger before_stmt_trigger
+	before update on stmt_trig_on_empty_upd
+	execute function update_stmt_notice();
+create trigger before_stmt_trigger
+	before update on stmt_trig_on_empty_upd1
+	execute function update_stmt_notice();
+-- inherited update
+update stmt_trig_on_empty_upd set a = a where false returning a+1 as aa;
+-- simple update
+update stmt_trig_on_empty_upd1 set a = a where false returning a+1 as aa;
+drop table stmt_trig_on_empty_upd cascade;
+drop function update_stmt_notice;