tickets: 3369

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id	created	changetime	last_pulled_from_trac	stage	status	component	type	severity	version	resolution	summary	description	owner	reporter	keywords	easy	has_patch	needs_better_patch	needs_tests	needs_docs	ui_ux
3369	2007-01-26 06:31:13	2007-09-16 16:13:51	2022-03-06 03:28:31.822843	Design decision needed	closed	Database layer (models, ORM)			dev	duplicate	reverse caching of foreign keys	It would be nice if Django were to cache the reverse value of foreign keys when they're looked up. That might not be entirely clear, so let me give an example: {{{ class Company(Model): name = models.CharField(maxlength=100) class Employee(Model): company = models.ForeignKey(Company) c = Company.objects.all()[0] e = c.employee_set.all()[0] # e now really must have a company of c... there's no reason it wouldn't be c e.company # accesses the database }}} I tried implementing this, but got lost in some of the model code. My approach was to use an auto_cache 'filter' for QuerySets. The above code would look like this: {{{ c = Company.objects.all()[0] e = c.employee_set.auto_cache(company=c).all()[0] e.company # no database accesses }}} Which eventually I would have made automatic for all sets. I got far enough to realize that each foreign key will potentially query the database even after an attribute has explicitly been assigned. For example: {{{ c = Company.objects.all()[0] e = c.employee_set.all()[0] new_company = Company() e.company = new_company e.company == new_company # database accesses for e.company and not equal to the new object }}} I'd love to see a feature like this, so if it's not something that you all want to implement, point me in the right direction.	nobody	wbyoung@mcdonogh.org		0	1	0	0	0	0