(see attached code to prepare)

analyze select * from noCondition;

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

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

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

|    1 | SIMPLE      | a     | const | PRIMARY       | PRIMARY | 4       | const | 1    | NULL   |   100.00 |       NULL | Using index |

|    1 | SIMPLE      | b     | ALL   | NULL          | NULL    | NULL    | NULL  | 1    | 1.00   |   100.00 |     100.00 | Using where |

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

analyze select * from forceConditionU;

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

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

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

|    1 | SIMPLE      | a     | const | PRIMARY       | PRIMARY | 4       | const | 1    | NULL   |   100.00 |       NULL | Using index |

|    1 | SIMPLE      | b     | ALL   | NULL          | NULL    | NULL    | NULL  | 1    | 1.00   |   100.00 |     100.00 | Using where |

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

analyze select * from forceConditionM;

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

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

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

|    1 | SIMPLE      | a     | const | PRIMARY       | PRIMARY | 4       | const | 1    | NULL   |   100.00 |       NULL | Using index |

|    1 | SIMPLE      | b     | ALL   | NULL          | NULL    | NULL    | NULL  | 1    | 1.00   |   100.00 |     100.00 | Using where |

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

analyze select straight_join `a`.`id` AS `id` from (`b` join `a` on(`b`.`notIndexed` = `a`.`id`)) where `a`.`id` = 1;

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

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

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

|    1 | SIMPLE      | b     | ALL   | NULL          | NULL    | NULL    | NULL  | 1    | 1.00   |   100.00 |     100.00 | Using where |

|    1 | SIMPLE      | a     | const | PRIMARY       | PRIMARY | 4       | const | 1    | 1.00   |   100.00 |     100.00 | Using index |

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