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
27149	Allow using a subquery in QuerySet.filter()	MikiSoft	Matthew Schinckel	"The following function is used for filtering by generic relation (and also by one column in the model where it is) which isn't natively supported by Django.

{{{
APP_LABEL = os.path.basename(os.path.dirname(__file__))
def generic_rel_filter(model, target, column, id):
    return model.objects.extra(where=['''
        {app_label}_{model}.id in (select object_id
        from {app_label}_{target}
        where content_type_id = (select id from django_content_type where model = '{model}')
            and {column} = {id})'''.format(app_label=APP_LABEL, model=model.__name__.lower(), target=target, column=column, id=id)])
}}}

''Example:'' If I have Event and Like model, and the second one has generic relation to the first one (i.e. it has `content_type`, `object_id` and `content_object` fields), then if I want to get all events which current user liked, I would just make this call in a view: `generic_rel_filter(Event, 'like', 'person', self.request.user.pk)`

'''Note that this function isn't intended to be used with user specified parameters, otherwise it's prone to SQL injection attacks.'''

P.S. It can be done with ORM but then it would go with three queries, which is much slower than the method above (which uses only one query to do the same): `Event.objects.filter(pk__in=Like.objects.filter(content_type=ContentType.objects.get(model='event'), person=self.request.user).values_list('object_id', flat=True))`"	New feature	closed	Database layer (models, ORM)		Normal	fixed	Queryset SubQuery Exists		Ready for checkin	1	0	0	0	0	0