Fix RETURNING to work correctly with partition tuple routing.

In ExecInsert(), do not switch back to the root partitioned table
ResultRelInfo until after we finish ExecProcessReturning(), so that
RETURNING projection is done using the partition's descriptor.  For
the projection to work correctly, we must initialize the same for each
leaf partition during ModifyTableState initialization.

Amit Langote

src/backend/catalog/partition.c

@@ -883,7 +883,8 @@ get_qual_from_partbound(Relation rel, Relation parent, Node *bound)
  * different from the parent's.
  */
 List *
-map_partition_varattnos(List *expr, Relation partrel, Relation parent)
+map_partition_varattnos(List *expr, int target_varno,
+						Relation partrel, Relation parent)
 {
 	TupleDesc	tupdesc = RelationGetDescr(parent);
 	AttrNumber	attno;
@@ -908,7 +909,7 @@ map_partition_varattnos(List *expr, Relation partrel, Relation parent)
 	}
 
 	expr = (List *) map_variable_attnos((Node *) expr,
-										1, 0,
+										target_varno, 0,
 										part_attnos,
 										tupdesc->natts,
 										&found_whole_row);
@@ -1540,8 +1541,9 @@ generate_partition_qual(Relation rel)
 	 * Change Vars to have partition's attnos instead of the parent's.
 	 * We do this after we concatenate the parent's quals, because
 	 * we want every Var in it to bear this relation's attnos.
+	 * It's safe to assume varno = 1 here.
 	 */
-	result = map_partition_varattnos(result, rel, parent);
+	result = map_partition_varattnos(result, 1, rel, parent);
 
 	/* Save a copy in the relcache */
 	oldcxt = MemoryContextSwitchTo(CacheMemoryContext);

src/backend/commands/tablecmds.c

@@ -13454,6 +13454,7 @@ ATExecAttachPartition(List **wqueue, Relation rel, PartitionCmd *cmd)
 			constr = linitial(partConstraint);
 			my_constr = make_ands_implicit((Expr *) constr);
 			tab->partition_constraint = map_partition_varattnos(my_constr,
+																1,
 																part_rel,
 																rel);
 			/* keep our lock until commit */

src/backend/executor/execMain.c

@@ -1279,10 +1279,10 @@ InitResultRelInfo(ResultRelInfo *resultRelInfo,
 		/*
 		 * This is not our own partition constraint, but rather an ancestor's.
 		 * So any Vars in it bear the ancestor's attribute numbers.  We must
-		 * switch them to our own.
+		 * switch them to our own. (dummy varno = 1)
 		 */
 		if (partition_check != NIL)
-			partition_check = map_partition_varattnos(partition_check,
+			partition_check = map_partition_varattnos(partition_check, 1,
 													  resultRelationDesc,
 													  partition_root);
 	}

src/backend/executor/nodeModifyTable.c

@@ -262,7 +262,8 @@ ExecInsert(ModifyTableState *mtstate,
 	Relation	resultRelationDesc;
 	Oid			newId;
 	List	   *recheckIndexes = NIL;
-	TupleTableSlot *oldslot = slot;
+	TupleTableSlot *oldslot = slot,
+				   *result = NULL;
 
 	/*
 	 * get the heap tuple out of the tuple table slot, making sure we have a
@@ -574,12 +575,6 @@ ExecInsert(ModifyTableState *mtstate,
 
 	list_free(recheckIndexes);
 
-	if (saved_resultRelInfo)
-	{
-		resultRelInfo = saved_resultRelInfo;
-		estate->es_result_relation_info = resultRelInfo;
-	}
-
 	/*
 	 * Check any WITH CHECK OPTION constraints from parent views.  We are
 	 * required to do this after testing all constraints and uniqueness
@@ -597,9 +592,12 @@ ExecInsert(ModifyTableState *mtstate,
 
 	/* Process RETURNING if present */
 	if (resultRelInfo->ri_projectReturning)
-		return ExecProcessReturning(resultRelInfo, slot, planSlot);
+		result = ExecProcessReturning(resultRelInfo, slot, planSlot);
 
-	return NULL;
+	if (saved_resultRelInfo)
+		estate->es_result_relation_info = saved_resultRelInfo;
+
+	return result;
 }
 
 /* ----------------------------------------------------------------
@@ -1786,6 +1784,7 @@ ExecInitModifyTable(ModifyTable *node, EState *estate, int eflags)
 	{
 		TupleTableSlot *slot;
 		ExprContext *econtext;
+		List		*returningList;
 
 		/*
 		 * Initialize result tuple slot and assign its rowtype using the first
@@ -1818,6 +1817,32 @@ ExecInitModifyTable(ModifyTable *node, EState *estate, int eflags)
 									 resultRelInfo->ri_RelationDesc->rd_att);
 			resultRelInfo++;
 		}
+
+		/*
+		 * Build a projection for each leaf partition rel.  Note that we
+		 * didn't build the returningList for each partition within the
+		 * planner, but simple translation of the varattnos for each
+		 * partition will suffice.  This only occurs for the INSERT case;
+		 * UPDATE/DELETE are handled above.
+		 */
+		resultRelInfo = mtstate->mt_partitions;
+		returningList = linitial(node->returningLists);
+		for (i = 0; i < mtstate->mt_num_partitions; i++)
+		{
+			Relation	partrel = resultRelInfo->ri_RelationDesc;
+			List	   *rlist,
+					   *rliststate;
+
+			/* varno = node->nominalRelation */
+			rlist = map_partition_varattnos(returningList,
+											node->nominalRelation,
+											partrel, rel);
+			rliststate = (List *) ExecInitExpr((Expr *) rlist, &mtstate->ps);
+			resultRelInfo->ri_projectReturning =
+				ExecBuildProjectionInfo(rliststate, econtext, slot,
+									 resultRelInfo->ri_RelationDesc->rd_att);
+			resultRelInfo++;
+		}
 	}
 	else
 	{

src/include/catalog/partition.h

@@ -77,7 +77,8 @@ extern bool partition_bounds_equal(PartitionKey key,
 extern void check_new_partition_bound(char *relname, Relation parent, Node *bound);
 extern Oid get_partition_parent(Oid relid);
 extern List *get_qual_from_partbound(Relation rel, Relation parent, Node *bound);
-extern List *map_partition_varattnos(List *expr, Relation partrel, Relation parent);
+extern List *map_partition_varattnos(List *expr, int target_varno,
+						Relation partrel, Relation parent);
 extern List *RelationGetPartitionQual(Relation rel);
 
 /* For tuple routing */

src/test/regress/expected/insert.out

@@ -364,5 +364,27 @@ DETAIL:  Failing row contains (1, 2).
 insert into p1 (a, b) values (2, 3);
 ERROR:  new row for relation "p11" violates partition constraint
 DETAIL:  Failing row contains (3, 2).
+-- check that RETURNING works correctly with tuple-routing
+alter table p drop constraint check_b;
+create table p12 partition of p1 for values from (5) to (10);
+create table p2 (b int not null, a int not null);
+alter table p attach partition p2 for values from (1, 10) to (1, 20);
+create table p3 partition of p for values from (1, 20) to (1, 30);
+create table p4 (like p);
+alter table p4 drop a;
+alter table p4 add a int not null;
+alter table p attach partition p4 for values from (1, 30) to (1, 40);
+with ins (a, b, c) as
+  (insert into p (b, a) select s.a, 1 from generate_series(2, 39) s(a) returning tableoid::regclass, *)
+  select a, b, min(c), max(c) from ins group by a, b order by 1;
+  a  | b | min | max 
+-----+---+-----+-----
+ p11 | 1 |   2 |   4
+ p12 | 1 |   5 |   9
+ p2  | 1 |  10 |  19
+ p3  | 1 |  20 |  29
+ p4  | 1 |  30 |  39
+(5 rows)
+
 -- cleanup
-drop table p, p1, p11;
+drop table p, p1, p11, p12, p2, p3, p4;

src/test/regress/sql/insert.sql

@@ -226,5 +226,19 @@ insert into p values (1, 2);
 -- selected by tuple-routing
 insert into p1 (a, b) values (2, 3);
 
+-- check that RETURNING works correctly with tuple-routing
+alter table p drop constraint check_b;
+create table p12 partition of p1 for values from (5) to (10);
+create table p2 (b int not null, a int not null);
+alter table p attach partition p2 for values from (1, 10) to (1, 20);
+create table p3 partition of p for values from (1, 20) to (1, 30);
+create table p4 (like p);
+alter table p4 drop a;
+alter table p4 add a int not null;
+alter table p attach partition p4 for values from (1, 30) to (1, 40);
+with ins (a, b, c) as
+  (insert into p (b, a) select s.a, 1 from generate_series(2, 39) s(a) returning tableoid::regclass, *)
+  select a, b, min(c), max(c) from ins group by a, b order by 1;
+
 -- cleanup
-drop table p, p1, p11;
+drop table p, p1, p11, p12, p2, p3, p4;