Bug# 15968 - Partitions: crash when insert with f1 = -1 into partition by hash(f1)

fixed


mysql-test/r/partition_hash.result:
  results for newly added test.
mysql-test/t/partition_hash.test:
  test case for inserting a value into a hash that would generate a negative value
sql/sql_partition.cc:
  fields that generate a negative value would also generate a negative
  part_id which doesn't index into the m_file array to well.

mysql-test/r/partition_hash.result

@@ -64,3 +64,9 @@ primary key(a,b))
 partition by key (a)
 (partition x1);
 drop table t1;
+CREATE TABLE t1 (f1 INTEGER, f2 char(20)) ENGINE = 'MYISAM' PARTITION BY HASH(f1) PARTITIONS 2;
+INSERT INTO t1 SET f1 = 0 - 1, f2 = '#######';
+select * from t1;
+f1	f2
+-1	#######
+drop table t1;

mysql-test/t/partition_hash.test

@@ -75,3 +75,12 @@ partition by key (a)
 (partition x1);
 
 drop table t1;
+
+#
+# Bug# 15968 - crash when INSERT with f1 = -1 into partition by hash(f1)
+#
+CREATE TABLE t1 (f1 INTEGER, f2 char(20)) ENGINE = 'MYISAM' PARTITION BY HASH(f1) PARTITIONS 2;
+INSERT INTO t1 SET f1 = 0 - 1, f2 = '#######';
+select * from t1;
+drop table t1;
+

sql/sql_partition.cc

@@ -2327,7 +2327,8 @@ static uint32 get_part_id_hash(uint no_parts,
                                Item *part_expr)
 {
   DBUG_ENTER("get_part_id_hash");
-  DBUG_RETURN((uint32)(part_expr->val_int() % no_parts));
+  longlong int_hash_id= part_expr->val_int() % no_parts;
+  DBUG_RETURN(int_hash_id < 0 ? -int_hash_id : int_hash_id);
 }