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]>