development.sql

mysql> EXPLAIN SELECT count(DISTINCT `competition_entries`.id) AS count_all FROM `competition_entries` LEFT OUTER JOIN `videos` ON `videos`.attachable_id = `competition_entries`.id AND `videos`.attachable_type = 'CompetitionEntry' LEFT OUTER JOIN `moderations` ON `moderations`.moderated_id = `competition_entries`.id AND `moderations`.moderated_type = 'CompetitionEntry' LEFT OUTER JOIN `users` ON `users`.id = `competition_entries`.user_id INNER JOIN `images` ON `images`.attachable_id = `competition_entries`.id AND `images`.attachable_type = 'CompetitionEntry' WHERE (moderations.state = 0) ;
+----+-------------+---------------------+--------+-----------------------------------------------------------------------+-----------------------------------+---------+--------------------------------------------------+------+-------------+
| id | select_type | table               | type   | possible_keys                                                         | key                               | key_len | ref                                              | rows | Extra       |
+----+-------------+---------------------+--------+-----------------------------------------------------------------------+-----------------------------------+---------+--------------------------------------------------+------+-------------+
|  1 | SIMPLE      | images              | ref    | index_images_on_attachable_id,index_images_on_attachable_type         | index_images_on_attachable_type   | 768     | const                                            |   13 | Using where | 
|  1 | SIMPLE      | moderations         | ref    | index_moderations_on_moderated_type,index_moderations_on_moderated_id | index_moderations_on_moderated_id | 5       | benetton_development.images.attachable_id        |    1 | Using where | 
|  1 | SIMPLE      | competition_entries | eq_ref | PRIMARY                                                               | PRIMARY                           | 4       | benetton_development.images.attachable_id        |    1 |             | 
|  1 | SIMPLE      | videos              | ref    | index_videos_on_attachable_id,index_videos_on_attachable_type         | index_videos_on_attachable_id     | 5       | benetton_development.moderations.moderated_id    |    1 |             | 
|  1 | SIMPLE      | users               | eq_ref | PRIMARY                                                               | PRIMARY                           | 4       | benetton_development.competition_entries.user_id |    1 | Using index | 
+----+-------------+---------------------+--------+-----------------------------------------------------------------------+-----------------------------------+---------+--------------------------------------------------+------+-------------+

production.sql

mysql> EXPLAIN SELECT count(DISTINCT `competition_entries`.id) AS count_all FROM `competition_entries` LEFT OUTER JOIN `videos` ON `videos`.attachable_id = `competition_entries`.id AND `videos`.attachable_type = 'CompetitionEntry' LEFT OUTER JOIN `moderations` ON `moderations`.moderated_id = `competition_entries`.id AND `moderations`.moderated_type = 'CompetitionEntry' LEFT OUTER JOIN `users` ON `users`.id = `competition_entries`.user_id INNER JOIN `images` ON `images`.attachable_id = `competition_entries`.id AND `images`.attachable_type = 'CompetitionEntry' WHERE (moderations.state = 0) ;
+----+-------------+---------------------+--------+--------------------------------------------------------------------------------------------------+-----------------------------------+---------+-------------------------------------------------+-------+-------------+
| id | select_type | table               | type   | possible_keys                                                                                    | key                               | key_len | ref                                             | rows  | Extra       |
+----+-------------+---------------------+--------+--------------------------------------------------------------------------------------------------+-----------------------------------+---------+-------------------------------------------------+-------+-------------+
|  1 | SIMPLE      | images              | ref    | index_images_on_attachable_id,index_images_on_attachable_type                                    | index_images_on_attachable_type   | 768     | const                                           | 57460 | Using where | 
|  1 | SIMPLE      | moderations         | ref    | index_moderations_on_moderated_type,index_moderations_on_moderated_id,index_moderations_on_state | index_moderations_on_moderated_id | 5       | benetton_production.images.attachable_id        |     1 | Using where | 
|  1 | SIMPLE      | competition_entries | eq_ref | PRIMARY                                                                                          | PRIMARY                           | 4       | benetton_production.images.attachable_id        |     1 |             | 
|  1 | SIMPLE      | videos              | ref    | index_videos_on_attachable_id,index_videos_on_attachable_type                                    | index_videos_on_attachable_id     | 5       | benetton_production.images.attachable_id        |     1 |             | 
|  1 | SIMPLE      | users               | eq_ref | PRIMARY                                                                                          | PRIMARY                           | 4       | benetton_production.competition_entries.user_id |     1 | Using index | 
+----+-------------+---------------------+--------+--------------------------------------------------------------------------------------------------+-----------------------------------+---------+-------------------------------------------------+-------+-------------+
5 rows in set (0.01 sec)