=== modified file 'mysql-test/r/key.result'
--- mysql-test/r/key.result	2013-11-20 11:05:39 +0000
+++ mysql-test/r/key.result	2014-03-13 12:15:10 +0000
@@ -612,3 +612,30 @@ SELECT 1 as RES FROM t1 AS t1_outer WHER
 (SELECT max(b) FROM t1 GROUP BY a HAVING a < 2) > 12;
 RES
 DROP TABLE t1;
+#
+# Bug#18144: Cost with FORCE/USE index seems incorrect in some cases.
+#
+# We are interested in showing that the cost for the last plan is higher
+# than for the preceding two plans.
+#
+CREATE TABLE t1( a INT, b INT, KEY( a ) );
+INSERT INTO t1 values (1, 2), (1, 3), (2, 3), (2, 4), (3, 4), (3, 5);
+EXPLAIN SELECT a, SUM( b ) FROM t1 GROUP BY a;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	6	Using temporary; Using filesort
+SHOW STATUS LIKE 'Last_query_cost';
+Variable_name	Value
+Last_query_cost	9.212184
+EXPLAIN SELECT a, SUM( b ) FROM t1 USE INDEX( a ) GROUP BY a;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	6	Using temporary; Using filesort
+SHOW STATUS LIKE 'Last_query_cost';
+Variable_name	Value
+Last_query_cost	9.212184
+EXPLAIN SELECT a, SUM( b ) FROM t1 FORCE INDEX( a ) GROUP BY a;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	index	NULL	a	5	NULL	6	
+SHOW STATUS LIKE 'Last_query_cost';
+Variable_name	Value
+Last_query_cost	14.199000
+DROP TABLE t1;

=== modified file 'mysql-test/t/key.test'
--- mysql-test/t/key.test	2007-12-05 19:33:36 +0000
+++ mysql-test/t/key.test	2014-03-13 11:32:19 +0000
@@ -561,3 +561,23 @@ SELECT 1 as RES FROM t1 AS t1_outer WHER
   (SELECT max(b) FROM t1 GROUP BY a HAVING a < 2) > 12;
 
 DROP TABLE t1;
+
+--echo #
+--echo # Bug#18144: Cost with FORCE/USE index seems incorrect in some cases.
+--echo #
+--echo # We are interested in showing that the cost for the last plan is higher
+--echo # than for the preceding two plans.
+--echo #
+CREATE TABLE t1( a INT, b INT, KEY( a ) );  
+INSERT INTO t1 values (1, 2), (1, 3), (2, 3), (2, 4), (3, 4), (3, 5);
+
+EXPLAIN SELECT a, SUM( b ) FROM t1 GROUP BY a;
+SHOW STATUS LIKE 'Last_query_cost';
+
+EXPLAIN SELECT a, SUM( b ) FROM t1 USE INDEX( a ) GROUP BY a;
+SHOW STATUS LIKE 'Last_query_cost';
+
+EXPLAIN SELECT a, SUM( b ) FROM t1 FORCE INDEX( a ) GROUP BY a;
+SHOW STATUS LIKE 'Last_query_cost';
+
+DROP TABLE t1;