Improve error message when skipping scan of default partition.

It seems like a good idea to clearly distinguish between skipping the
scan of the new partition itself and skipping the scan of the default
partition.

Amit Langote

Discussion: http://postgr.es/m/1f08b844-0078-aa8d-452e-7af3bf77d05f@lab.ntt.co.jp

src/backend/commands/tablecmds.c

@@ -13635,9 +13635,14 @@ ValidatePartitionConstraints(List **wqueue, Relation scanrel,
 	 */
 	if (PartConstraintImpliedByRelConstraint(scanrel, partConstraint))
 	{
-		ereport(INFO,
-				(errmsg("partition constraint for table \"%s\" is implied by existing constraints",
-						RelationGetRelationName(scanrel))));
+		if (!validate_default)
+			ereport(INFO,
+					(errmsg("partition constraint for table \"%s\" is implied by existing constraints",
+							RelationGetRelationName(scanrel))));
+		else
+			ereport(INFO,
+					(errmsg("updated partition constraint for default partition \"%s\" is implied by existing constraints",
+							RelationGetRelationName(scanrel))));
 		return;
 	}
 

src/test/regress/expected/alter_table.out

@@ -3436,7 +3436,7 @@ ALTER TABLE part_7 ATTACH PARTITION part_7_a_null FOR VALUES IN ('a', null);
 INFO:  partition constraint for table "part_7_a_null" is implied by existing constraints
 ALTER TABLE list_parted2 ATTACH PARTITION part_7 FOR VALUES IN (7);
 INFO:  partition constraint for table "part_7" is implied by existing constraints
-INFO:  partition constraint for table "list_parted2_def" is implied by existing constraints
+INFO:  updated partition constraint for default partition "list_parted2_def" is implied by existing constraints
 -- Same example, but check this time that the constraint correctly detects
 -- violating rows
 ALTER TABLE list_parted2 DETACH PARTITION part_7;
@@ -3450,7 +3450,7 @@ SELECT tableoid::regclass, a, b FROM part_7 order by a;
 (2 rows)
 
 ALTER TABLE list_parted2 ATTACH PARTITION part_7 FOR VALUES IN (7);
-INFO:  partition constraint for table "list_parted2_def" is implied by existing constraints
+INFO:  updated partition constraint for default partition "list_parted2_def" is implied by existing constraints
 ERROR:  partition constraint is violated by some row
 -- check that leaf partitions of default partition are scanned when
 -- attaching a partitioned table.