Fix inherited UPDATE/DELETE with UNION ALL subqueries.

Fix an oversight in commit b3aaf9081a: we do
indeed need to process the planner's append_rel_list when copying RTE
subqueries, because if any of them were flattenable UNION ALL subqueries,
the append_rel_list shows which subquery RTEs were pulled up out of which
other ones.  Without this, UNION ALL subqueries aren't correctly inserted
into the update plans for inheritance child tables after the first one,
typically resulting in no update happening for those child table(s).
Per report from Victor Yegorov.

Experimentation with this case also exposed a fault in commit
a7b965382c: if an inherited UPDATE/DELETE
was proven totally dummy by constraint exclusion, we might arrive at
add_rtes_to_flat_rtable with root->simple_rel_array being NULL.  This
should be interpreted as not having any RelOptInfos.  I chose to code
the guard as a check against simple_rel_array_size, so as to also
provide some protection against indexing off the end of the array.

Back-patch to 9.2 where the faulty code was added.

src/backend/optimizer/plan/planner.c

@@ -848,6 +848,13 @@ inheritance_planner(PlannerInfo *root)
 		 */
 		subroot.rowMarks = (List *) copyObject(root->rowMarks);
 
+		/*
+		 * The append_rel_list likewise might contain references to subquery
+		 * RTEs (if any subqueries were flattenable UNION ALLs).  So prepare
+		 * to apply ChangeVarNodes to that, too.
+		 */
+		subroot.append_rel_list = (List *) copyObject(root->append_rel_list);
+
 		/*
 		 * Add placeholders to the child Query's rangetable list to fill the
 		 * RT indexes already reserved for subqueries in previous children.
@@ -888,6 +895,7 @@ inheritance_planner(PlannerInfo *root)
 					newrti = list_length(subroot.parse->rtable) + 1;
 					ChangeVarNodes((Node *) subroot.parse, rti, newrti, 0);
 					ChangeVarNodes((Node *) subroot.rowMarks, rti, newrti, 0);
+					ChangeVarNodes((Node *) subroot.append_rel_list, rti, newrti, 0);
 					rte = copyObject(rte);
 					subroot.parse->rtable = lappend(subroot.parse->rtable,
 													rte);
@@ -896,7 +904,6 @@ inheritance_planner(PlannerInfo *root)
 			}
 		}
 
-		/* We needn't modify the child's append_rel_list */
 		/* There shouldn't be any OJ or LATERAL info to translate, as yet */
 		Assert(subroot.join_info_list == NIL);
 		Assert(subroot.lateral_info_list == NIL);

src/backend/optimizer/plan/setrefs.c

@@ -280,7 +280,8 @@ add_rtes_to_flat_rtable(PlannerInfo *root, bool recursing)
 		 * RTEs without matching RelOptInfos, as they likewise have been
 		 * pulled up.
 		 */
-		if (rte->rtekind == RTE_SUBQUERY && !rte->inh)
+		if (rte->rtekind == RTE_SUBQUERY && !rte->inh &&
+			rti < root->simple_rel_array_size)
 		{
 			RelOptInfo *rel = root->simple_rel_array[rti];
 

src/test/regress/expected/inherit.out

@@ -557,8 +557,7 @@ insert into bar2 values(2,2,2);
 insert into bar2 values(3,3,3);
 insert into bar2 values(4,4,4);
 update bar set f2 = f2 + 100 where f1 in (select f1 from foo);
-SELECT relname, bar.* FROM bar, pg_class where bar.tableoid = pg_class.oid
-order by 1,2;
+select tableoid::regclass::text as relname, bar.* from bar order by 1,2;
  relname | f1 | f2  
 ---------+----+-----
  bar     |  1 | 101
@@ -571,6 +570,24 @@ order by 1,2;
  bar2    |  4 |   4
 (8 rows)
 
+-- Check UPDATE with inherited target and an appendrel subquery
+update bar set f2 = f2 + 100
+from
+  ( select f1 from foo union all select f1+3 from foo ) ss
+where bar.f1 = ss.f1;
+select tableoid::regclass::text as relname, bar.* from bar order by 1,2;
+ relname | f1 | f2  
+---------+----+-----
+ bar     |  1 | 201
+ bar     |  2 | 202
+ bar     |  3 | 203
+ bar     |  4 | 104
+ bar2    |  1 | 201
+ bar2    |  2 | 202
+ bar2    |  3 | 203
+ bar2    |  4 | 104
+(8 rows)
+
 /* Test multiple inheritance of column defaults */
 CREATE TABLE firstparent (tomorrow date default now()::date + 1);
 CREATE TABLE secondparent (tomorrow date default  now() :: date  +  1);

src/test/regress/sql/inherit.sql

@@ -118,8 +118,15 @@ insert into bar2 values(4,4,4);
 
 update bar set f2 = f2 + 100 where f1 in (select f1 from foo);
 
-SELECT relname, bar.* FROM bar, pg_class where bar.tableoid = pg_class.oid
-order by 1,2;
+select tableoid::regclass::text as relname, bar.* from bar order by 1,2;
+
+-- Check UPDATE with inherited target and an appendrel subquery
+update bar set f2 = f2 + 100
+from
+  ( select f1 from foo union all select f1+3 from foo ) ss
+where bar.f1 = ss.f1;
+
+select tableoid::regclass::text as relname, bar.* from bar order by 1,2;
 
 /* Test multiple inheritance of column defaults */