id,summary,reporter,owner,description,type,status,component,version,severity,resolution,keywords,cc,stage,has_patch,needs_docs,needs_tests,needs_better_patch,easy,ui_ux 2306,Many-to-many queries very slow on MySQL 3.23.58,anonymous,nobody,"We have a MySQL 3.23.58 database with about 1000 Room and Photo objects, connected by a many-to-many relationship. Given a room r, asking Django to evaluate r.photos.all() runs an explicit join: {{{ SELECT `kords3_photo`.`id`,`kords3_photo`.`image` FROM `kords3_photo` LEFT OUTER JOIN `kords3_room_photos` AS `m2m_kords3_photo__room` ON `kords3_photo`.`id` = `m2m_kords3_photo__room`.`photo_id` WHERE (`m2m_kords3_photo__room`.`room_id` = 1) ORDER BY `kords3_photo`.`image` ASC }}} which takes around 1 second, when the same query rewritten as an implicit join: {{{ SELECT `kords3_photo`.`id`,`kords3_photo`.`image` FROM `kords3_photo` , `kords3_room_photos` WHERE `kords3_photo`.`id` = `kords3_room_photos`.`photo_id` AND `kords3_room_photos`.`room_id` = 1 ORDER BY `kords3_photo`.`image` ASC }}} would take under a millisecond. ",defect,closed,"Database layer (models, ORM)",dev,normal,fixed,qs-rf-fixed,mir@… freakboy3742@…,Accepted,0,0,0,0,0,0