Fixed bug lp:888456

Analysis:
The class member QUICK_GROUP_MIN_MAX_SELECT::seen_first_key
was not reset between subquery re-executions. Thus each
subsequent execution continued from the group that was
reached by the previous subquery execution. As a result
loose scan reached end of file much earlier, and returned
empty result where it shouldn't.

Solution:
Reset seen_first_key before each re-execution of the
loose scan.

mysql-test/r/group_min_max.result

@@ -2780,4 +2780,21 @@ ORDER BY min_a;
 min_a
 NULL
 DROP TABLE t1;
+#
+# LP BUG#888456 Wrong result with DISTINCT , ANY , subquery_cache=off , NOT NULL
+#
+CREATE TABLE t1 ( a int NOT NULL) ;
+INSERT INTO t1 VALUES (28),(29),(9);
+CREATE TABLE t2 ( a int, KEY (a)) ;
+INSERT INTO t2 VALUES (1),(1),(1),(4),(4),(5),(5),(8),(8),(9);
+explain select (select t2.a from t2 where t2.a >= t1.a group by t2.a) from t1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	3	
+2	DEPENDENT SUBQUERY	t2	range	a	a	5	NULL	6	Using where; Using index for group-by
+select (select t2.a from t2 where t2.a >= t1.a group by t2.a) from t1;
+(select t2.a from t2 where t2.a >= t1.a group by t2.a)
+NULL
+NULL
+9
+drop table t1, t2;
 End of 5.1 tests

mysql-test/t/group_min_max.test

@@ -1099,5 +1099,19 @@ ORDER BY min_a;
 
 DROP TABLE t1;
 
+--echo #
+--echo # LP BUG#888456 Wrong result with DISTINCT , ANY , subquery_cache=off , NOT NULL
+--echo #
+
+CREATE TABLE t1 ( a int NOT NULL) ;
+INSERT INTO t1 VALUES (28),(29),(9);
+
+CREATE TABLE t2 ( a int, KEY (a)) ;
+INSERT INTO t2 VALUES (1),(1),(1),(4),(4),(5),(5),(8),(8),(9);
+
+explain select (select t2.a from t2 where t2.a >= t1.a group by t2.a) from t1;
+select (select t2.a from t2 where t2.a >= t1.a group by t2.a) from t1;
+
+drop table t1, t2;
 
 --echo End of 5.1 tests

sql/opt_range.cc

@@ -10627,6 +10627,7 @@ int QUICK_GROUP_MIN_MAX_SELECT::reset(void)
   int result;
   DBUG_ENTER("QUICK_GROUP_MIN_MAX_SELECT::reset");
 
+  seen_first_key= FALSE;
   if (!head->key_read)
   {
     doing_key_read= 1;