Fixed bug found by bar where we didn't properely check length of last argument for BETWEEN

This should not have caused any notable errors in most cases.

After fix, we are not using keys to solve MIN/MAX if the string used for comparision is longer thant the column-

mysql-test/r/group_min_max.result

@@ -3869,5 +3869,21 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	index	NULL	id	27	NULL	16	Using where; Using index
 DROP TABLE t1;
 #
+# MIN() optimization didn't work correctly with BETWEEN when using too
+# long strings.
+#
+create table t1 (a varchar(10), key (a)) engine=myisam;
+insert into t1 values("bar"),("Cafe");
+explain select min(a) from t1 where a between "a" and "Cafe2";
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Select tables optimized away
+explain select min(a) from t1 where a between "a" and "Cafeeeeeeeeeeeeeeeeeeeeeeeeee";
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	index	a	a	13	NULL	2	Using where; Using index
+explain select min(a) from t1 where a between "abbbbbbbbbbbbbbbbbbbb" and "Cafe2";
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	index	a	a	13	NULL	2	Using where; Using index
+drop table t1;
+#
 # End of 10.1 tests
 #

mysql-test/t/group_min_max.test

@@ -1596,6 +1596,17 @@ EXPLAIN SELECT id,MIN(a),MAX(a) FROM t1 WHERE a BETWEEN DATE'2001-01-04' AND
 EXPLAIN SELECT id,MIN(a),MAX(a) FROM t1 WHERE a BETWEEN     '2001-01-04' AND DATE'2001-01-05' GROUP BY id;
 DROP TABLE t1;
 
+--echo #
+--echo # MIN() optimization didn't work correctly with BETWEEN when using too
+--echo # long strings.
+--echo #
+
+create table t1 (a varchar(10), key (a)) engine=myisam;
+insert into t1 values("bar"),("Cafe");
+explain select min(a) from t1 where a between "a" and "Cafe2";
+explain select min(a) from t1 where a between "a" and "Cafeeeeeeeeeeeeeeeeeeeeeeeeee";
+explain select min(a) from t1 where a between "abbbbbbbbbbbbbbbbbbbb" and "Cafe2";
+drop table t1;
 
 --echo #
 --echo # End of 10.1 tests

sql/opt_sum.cc

@@ -578,7 +578,7 @@ bool simple_pred(Item_func *func_item, Item **args, bool *inv_order)
         if (!item->const_item())
           return 0;
         args[i]= item;
-        if (check_item1_shorter_item2(args[0], args[1]))
+        if (check_item1_shorter_item2(args[0], args[i]))
           return 0;
       }
     }