improve error message for case when default range interval is NULL

Author: funbringer

expected/pathman_interval.out

@@ -18,7 +18,7 @@ SELECT set_interval('test_interval.abc', NULL::INT2);
 
 /* pg_pathman shouldn't be able to create a new partition */
 INSERT INTO test_interval.abc VALUES (250);
-ERROR:  cannot find appropriate partition for key '250'
+ERROR:  cannot spawn new partition for key '250'
 /* Set a trivial interval */
 SELECT set_interval('test_interval.abc', 0);
 ERROR:  interval should not be trivial
@@ -61,7 +61,7 @@ SELECT set_interval('test_interval.abc', NULL::INT4);
 
 /* pg_pathman shouldn't be able to create a new partition */
 INSERT INTO test_interval.abc VALUES (250);
-ERROR:  cannot find appropriate partition for key '250'
+ERROR:  cannot spawn new partition for key '250'
 /* Set a trivial interval */
 SELECT set_interval('test_interval.abc', 0);
 ERROR:  interval should not be trivial
@@ -104,7 +104,7 @@ SELECT set_interval('test_interval.abc', NULL::INT8);
 
 /* pg_pathman shouldn't be able to create a new partition */
 INSERT INTO test_interval.abc VALUES (250);
-ERROR:  cannot find appropriate partition for key '250'
+ERROR:  cannot spawn new partition for key '250'
 /* Set a trivial interval */
 SELECT set_interval('test_interval.abc', 0);
 ERROR:  interval should not be trivial

src/partition_creation.c

@@ -408,9 +408,11 @@ create_partitions_for_value_internal(Oid relid, Datum value, Oid value_type,
 				/* Check if interval is set */
 				if (isnull[Anum_pathman_config_range_interval - 1])
 				{
-					elog(ERROR,
-						 "cannot find appropriate partition for key '%s'",
-						 datum_to_cstring(value, value_type));
+					ereport(ERROR,
+							(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+							 errmsg("cannot spawn new partition for key '%s'",
+									datum_to_cstring(value, value_type)),
+							 errdetail("default range interval is NULL")));
 				}
 
 				/* Retrieve interval as TEXT from tuple */