MariaDB []> explain UPDATE campaigns SET contacts = 5657, newleads = 904, redialscount = 43151, dnrcount = 513, dateupdated = NOW() WHERE id = 8257;
+------+-------------+-----------+-------+---------------+------+---------+------+------+---------------------------+
| id   | select_type | table     | type  | possible_keys | key  | key_len | ref  | rows | Extra                     |
+------+-------------+-----------+-------+---------------+------+---------+------+------+---------------------------+
|    1 | SIMPLE      | campaigns | range | PRIMARY,id    | id   | 4       | NULL | 1    | Using where; Using buffer |
+------+-------------+-----------+-------+---------------+------+---------+------+------+---------------------------+
1 row in set (0.001 sec)

MariaDB []> explain UPDATE campaigns **USE INDEX(PRIMARY)** SET contacts = 5657, newleads = 904, redialscount = 43151, dnrcount = 513, dateupdated = NOW() WHERE id = 8257;
+------+-------------+-----------+-------+---------------+---------+---------+------+------+-------------+
| id   | select_type | table     | type  | possible_keys | key     | key_len | ref  | rows | Extra       |
+------+-------------+-----------+-------+---------------+---------+---------+------+------+-------------+
|    1 | SIMPLE      | campaigns | range | PRIMARY       | PRIMARY | 4       | NULL | 1    | Using where |
+------+-------------+-----------+-------+---------------+---------+---------+------+------+-------------+