mysql> EXPLAIN SELECT COUNT(*) FROM `postman_message` LEFT OUTER JOIN `postman_message` T3 ON (`postman_message`.`thread_id` = T3.`id`) WHERE (`postman_message`.`id` IN (SELECT MAX(U0.`id`) AS `pk__max` FROM `postman_message` U0 WHERE (U0.`thread_id` IS NOT NULL AND (U0.`recipient_archived` = False AND U0.`moderation_status` = a AND U0.`recipient_id` = 201 AND U0.`recipient_deleted_at` IS NULL)) GROUP BY U0.`thread_id` ORDER BY NULL) OR ((`postman_message`.`recipient_archived` = False AND `postman_message`.`moderation_status` = a AND `postman_message`.`recipient_id` = 201 AND `postman_message`.`recipient_deleted_at` IS NULL) AND T3.`id` IS NULL));
ERROR 1054 (42S22): Unknown column 'a' in 'where clause'
mysql> EXPLAIN SELECT COUNT(*) FROM `postman_message` LEFT OUTER JOIN `postman_message` T3 ON (`postman_message`.`thread_id` = T3.`id`) WHERE (`postman_message`.`id` IN (SELECT MAX(U0.`id`) AS `pk__max` FROM `postman_message` U0 WHERE (U0.`thread_id` IS NOT NULL AND (U0.`recipient_archived` = False AND U0.`moderation_status` = "a" AND U0.`recipient_id` = 201 AND U0.`recipient_deleted_at` IS NULL)) GROUP BY U0.`thread_id` ORDER BY NULL) OR ((`postman_message`.`recipient_archived` = False AND `postman_message`.`moderation_status` = "a" AND `postman_message`.`recipient_id` = 201 AND `postman_message`.`recipient_deleted_at` IS NULL) AND T3.`id` IS NULL));
+----+--------------------+-----------------+--------+---------------------------------------------------+--------------------------+---------+-------------------------------------------+------+----------------------------------------------+
| id | select_type        | table           | type   | possible_keys                                     | key                      | key_len | ref                                       | rows | Extra                                        |
+----+--------------------+-----------------+--------+---------------------------------------------------+--------------------------+---------+-------------------------------------------+------+----------------------------------------------+
|  1 | PRIMARY            | postman_message | ALL    | postman_message_fcd09624                          | NULL                     | NULL    | NULL                                      | 3387 | Using where                                  |
|  1 | PRIMARY            | T3              | eq_ref | PRIMARY                                           | PRIMARY                  | 4       | teleforma_crfpa.postman_message.thread_id |    1 | Using where; Using index                     |
|  2 | DEPENDENT SUBQUERY | U0              | ref    | postman_message_fcd09624,postman_message_9a6ed576 | postman_message_fcd09624 | 5       | const                                     |    1 | Using where; Using temporary; Using filesort |
+----+--------------------+-----------------+--------+---------------------------------------------------+--------------------------+---------+-------------------------------------------+------+----------------------------------------------+
3 rows in set (0.00 sec)