create table t2 ( a char(10) not null, key(a)) engine=innodb;

insert into t2 values ('foo-123');

insert into t2 values ('bar-123');

insert into t2 values ('baz-123');

insert into t2 values ('abc-123');

insert into t2 values ('-1234');

insert into t2 values ('-99');

insert into t2 values ('-99999');

select max(a) from t2 where a < 432;

select max(a) from t2 ignore index(a) where a < 432;

MariaDB [j3]> select max(a) from t2 where a < 432;

+--------+

| max(a) |

+--------+

| -99999 |

+--------+

1 row in set (0.00 sec)

MariaDB [j3]> select max(a) from t2 ignore index(a) where a < 432;

+---------+

| max(a)  |

+---------+

| foo-123 |

+---------+

1 row in set, 4 warnings (0.01 sec)

MariaDB [j3]> explain select max(a) from t2 where a < 432;

+------+-------------+-------+------+---------------+------+---------+------+------+------------------------------+

| 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 |

+------+-------------+-------+------+---------------+------+---------+------+------+------------------------------+

1 row in set (0.00 sec)

MariaDB [j3]> explain select max(a) from t2 ignore index(a) where a < 432;

+------+-------------+-------+------+---------------+------+---------+------+------+-------------+

| id   | select_type | table | type | possible_keys | key  | key_len | ref  | rows | Extra       |

+------+-------------+-------+------+---------------+------+---------+------+------+-------------+

|    1 | SIMPLE      | t2    | ALL  | NULL          | NULL | NULL    | NULL |    7 | Using where |

+------+-------------+-------+------+---------------+------+---------+------+------+-------------+

1 row in set (0.01 sec)