Hint NO_MERGE(@qb_name) is accepted but has no effect

CREATE TABLE employees (

    emp_id INT PRIMARY KEY,

    emp_name VARCHAR(100),

    department VARCHAR(50)

);

CREATE TABLE salaries (

    emp_id INT,

    salary DECIMAL(10, 2),

    FOREIGN KEY (emp_id) REFERENCES employees(emp_id)

);

INSERT INTO employees (emp_id, emp_name, department) VALUES

 (101, 'Alice', 'Engineering'),

 (102, 'Bob', 'Engineering');

INSERT INTO salaries (emp_id, salary) VALUES

 (101, 120000.00),

 (102, 95000.00);

mysql>  EXPLAIN     SELECT  e.emp_name, s.salary FROM (select * from employees) e JOIN  (select * from salaries) s ON e.emp_id = s.emp_id ;

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

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

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

|  1 | SIMPLE      | employees | NULL       | ALL  | PRIMARY       | NULL   | NULL    | NULL                 |    5 |   100.00 | NULL  |

|  1 | SIMPLE      | salaries  | NULL       | ref  | emp_id        | emp_id | 5       | j11.employees.emp_id |    1 |   100.00 | NULL  |

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

mysql>  EXPLAIN     SELECT /*+ QB_NAME(foo) NO_MERGE(@`foo`) */ e.emp_name, s.salary FROM (select * from employees) e JOIN  (select * from salaries) s ON e.emp_id = s.emp_id ;

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

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

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

|  1 | PRIMARY     | <derived2> | NULL       | ALL  | NULL          | NULL        | NULL    | NULL     |    5 |   100.00 | NULL  |

|  1 | PRIMARY     | <derived3> | NULL       | ref  | <auto_key0>   | <auto_key0> | 5       | e.emp_id |    2 |   100.00 | NULL  |

|  3 | DERIVED     | salaries   | NULL       | ALL  | NULL          | NULL        | NULL    | NULL     |    5 |   100.00 | NULL  |

|  2 | DERIVED     | employees  | NULL       | ALL  | NULL          | NULL        | NULL    | NULL     |    5 |   100.00 | NULL  |

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

4 rows in set, 1 warning (0,00 sec)

Note (Code 1003): /* select#1 */ select /*+ QB_NAME(`foo`) NO_MERGE(@`foo`) */ `e`.`emp_name` AS `emp_name`,`s`.`salary` AS `salary` from (/* select#2 */ select `j11`.`employees`.`emp_id` AS `emp_id`,`j11`.`employees`.`emp_name` AS `emp_name`,`j11`.`employees`.`department` AS `department` from `j11`.`employees`) `e` join (/* select#3 */ select `j11`.`salaries`.`emp_id` AS `emp_id`,`j11`.`salaries`.`salary` AS `salary` from `j11`.`salaries`) `s` where (`s`.`emp_id` = `e`.`emp_id`)

MariaDB [j1]>  EXPLAIN EXTENDED SELECT /*+ QB_NAME(foo) NO_MERGE(@`foo`) */ e.emp_name, s.salary FROM (select * from employees) e JOIN  (select * from salaries) s ON e.emp_id = s.emp_id ;

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

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

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

|    1 | SIMPLE      | salaries  | ALL    | emp_id        | NULL    | NULL    | NULL               | 5    |   100.00 | Using where |

|    1 | SIMPLE      | employees | eq_ref | PRIMARY       | PRIMARY | 4       | j1.salaries.emp_id | 1    |   100.00 |             |

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

2 rows in set, 1 warning (0.002 sec)

Note (Code 1003): select /*+ QB_NAME(`foo`) NO_MERGE(@`foo`) */ `j1`.`employees`.`emp_name` AS `emp_name`,`j1`.`salaries`.`salary` AS `salary` from `j1`.`employees` join `j1`.`salaries` where `j1`.`employees`.`emp_id` = `j1`.`salaries`.`emp_id`