mysql:wikiadmin@db1052 [enwiki]> explain select 'en', user_editcount from user where user_name = 'Reedy';
+------+-------------+-------+-------+---------------+-----------+---------+-------+------+-------+
| id   | select_type | table | type  | possible_keys | key       | key_len | ref   | rows | Extra |
+------+-------------+-------+-------+---------------+-----------+---------+-------+------+-------+
|    1 | SIMPLE      | user  | const | user_name     | user_name | 257     | const |    1 |       |
+------+-------------+-------+-------+---------------+-----------+---------+-------+------+-------+
1 row in set (0.00 sec)

mysql:wikiadmin@db1052 [enwiki]> explain select 'en', user_editcount from user where user_name LIKE 'Reedy';
+------+-------------+-------+-------+---------------+-----------+---------+------+------+-----------------------+
| id   | select_type | table | type  | possible_keys | key       | key_len | ref  | rows | Extra                 |
+------+-------------+-------+-------+---------------+-----------+---------+------+------+-----------------------+
|    1 | SIMPLE      | user  | range | user_name     | user_name | 257     | NULL |    1 | Using index condition |
+------+-------------+-------+-------+---------------+-----------+---------+------+------+-----------------------+
1 row in set (0.01 sec)

mysql:wikiadmin@db1052 [enwiki]> explain select 'en', user_editcount from user where user_name LIKE 'Reedy%';
+------+-------------+-------+-------+---------------+-----------+---------+------+------+-----------------------+
| id   | select_type | table | type  | possible_keys | key       | key_len | ref  | rows | Extra                 |
+------+-------------+-------+-------+---------------+-----------+---------+------+------+-----------------------+
|    1 | SIMPLE      | user  | range | user_name     | user_name | 257     | NULL |   80 | Using index condition |
+------+-------------+-------+-------+---------------+-----------+---------+------+------+-----------------------+
1 row in set (0.00 sec)

mysql:wikiadmin@db1052 [enwiki]>