Fix improper NULL handling in list partitioning code.

The previous logic was wrong when the value was NULL but there was
no partition for NULL.

Amit Langote, reviewed by Jeevan Ladhe

Discussion: http://postgr.es/m/d64f8498-70eb-3c88-b56d-c54fd3b0500f@lab.ntt.co.jp

src/backend/catalog/partition.c

@@ -1729,10 +1729,14 @@ get_partition_for_tuple(PartitionDispatch *pd,
 						errmsg("range partition key of row contains null")));
 		}
 
-		if (partdesc->boundinfo->has_null && isnull[0])
-			/* Tuple maps to the null-accepting list partition */
+		/*
+		 * A null partition key is only acceptable if null-accepting list
+		 * partition exists.
+		 */
+		cur_index = -1;
+		if (isnull[0] && partdesc->boundinfo->has_null)
 			cur_index = partdesc->boundinfo->null_index;
-		else
+		else if (!isnull[0])
 		{
 			/* Else bsearch in partdesc->boundinfo */
 			bool		equal = false;

src/test/regress/expected/insert.out

@@ -365,6 +365,13 @@ DETAIL:  Failing row contains (1, 2).
 insert into mlparted1 (a, b) values (2, 3);
 ERROR:  new row for relation "mlparted11" violates partition constraint
 DETAIL:  Failing row contains (3, 2).
+-- check routing error through a list partitioned table when the key is null
+create table lparted_nonullpart (a int, b char) partition by list (b);
+create table lparted_nonullpart_a partition of lparted_nonullpart for values in ('a');
+insert into lparted_nonullpart values (1);
+ERROR:  no partition of relation "lparted_nonullpart" found for row
+DETAIL:  Partition key of the failing row contains (b) = (null).
+drop table lparted_nonullpart;
 -- check that RETURNING works correctly with tuple-routing
 alter table mlparted drop constraint check_b;
 create table mlparted12 partition of mlparted1 for values from (5) to (10);

src/test/regress/sql/insert.sql

@@ -226,6 +226,12 @@ insert into mlparted values (1, 2);
 -- selected by tuple-routing
 insert into mlparted1 (a, b) values (2, 3);
 
+-- check routing error through a list partitioned table when the key is null
+create table lparted_nonullpart (a int, b char) partition by list (b);
+create table lparted_nonullpart_a partition of lparted_nonullpart for values in ('a');
+insert into lparted_nonullpart values (1);
+drop table lparted_nonullpart;
+
 -- check that RETURNING works correctly with tuple-routing
 alter table mlparted drop constraint check_b;
 create table mlparted12 partition of mlparted1 for values from (5) to (10);