MySQL benchmark for database index on the Django' `auth_user.is_staff` field

gistfile1.sql

mysql> SELECT COUNT(*) FROM auth_user;
+----------+
| COUNT(*) |
+----------+
|    48158 |
+----------+
1 row in set (0.00 sec)

mysql> EXPLAIN SELECT COUNT(*) FROM auth_user WHERE is_staff = 1;
+----+-------------+-----------+------+---------------+------+---------+------+-------+-------------+
| id | select_type | table     | type | possible_keys | key  | key_len | ref  | rows  | Extra       |
+----+-------------+-----------+------+---------------+------+---------+------+-------+-------------+
|  1 | SIMPLE      | auth_user | ALL  | NULL          | NULL | NULL    | NULL | 48199 | Using where |
+----+-------------+-----------+------+---------------+------+---------+------+-------+-------------+
1 row in set (0.00 sec)

mysql> EXPLAIN SELECT COUNT(*) FROM auth_user WHERE is_staff = 0;
+----+-------------+-----------+------+---------------+------+---------+------+-------+-------------+
| id | select_type | table     | type | possible_keys | key  | key_len | ref  | rows  | Extra       |
+----+-------------+-----------+------+---------------+------+---------+------+-------+-------------+
|  1 | SIMPLE      | auth_user | ALL  | NULL          | NULL | NULL    | NULL | 48199 | Using where |
+----+-------------+-----------+------+---------------+------+---------+------+-------+-------------+

mysql> ALTER TABLE auth_user ADD INDEX (is_staff);
Query OK, 0 rows affected (0.10 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql> EXPLAIN SELECT COUNT(*) FROM auth_user WHERE is_staff = 0;
+----+-------------+-----------+------+---------------+----------+---------+-------+-------+-------------+
| id | select_type | table     | type | possible_keys | key      | key_len | ref   | rows  | Extra       |
+----+-------------+-----------+------+---------------+----------+---------+-------+-------+-------------+
|  1 | SIMPLE      | auth_user | ref  | is_staff      | is_staff | 1       | const | 24099 | Using index |
+----+-------------+-----------+------+---------------+----------+---------+-------+-------+-------------+
1 row in set (0.00 sec)

mysql> EXPLAIN SELECT COUNT(*) FROM auth_user WHERE is_staff = 1;
+----+-------------+-----------+------+---------------+----------+---------+-------+------+-------------+
| id | select_type | table     | type | possible_keys | key      | key_len | ref   | rows | Extra       |
+----+-------------+-----------+------+---------------+----------+---------+-------+------+-------------+
|  1 | SIMPLE      | auth_user | ref  | is_staff      | is_staff | 1       | const |   36 | Using index |
+----+-------------+-----------+------+---------------+----------+---------+-------+------+-------------+
1 row in set (0.00 sec)