#30355: Specifying custom manager doesn't work with prefetch -------------------------------+---------------------------------------- Reporter: Kyle Mulka | Owner: Akshat verma Type: Bug | Status: assigned Component: Documentation | Version: dev Severity: Normal | Resolution: Keywords: | Triage Stage: Accepted Has patch: 1 | Needs documentation: 1 Needs tests: 1 | Patch needs improvement: 1 Easy pickings: 1 | UI/UX: 1 -------------------------------+---------------------------------------- Changes (by Akshat verma):
* cc: Akshat verma (added) * needs_better_patch: 0 => 1 * needs_tests: 0 => 1 * easy: 0 => 1 * has_patch: 0 => 1 * ui_ux: 0 => 1 Old description: > When using prefetch and specifying a custom manager to use for a reverse > relation, Django doesn't filter correctly. Here's an example: > > {{{ > class Business(models.Model): > name = models.CharField(max_length=255) > > def approved_reviews(self): > return self.review_set(manager='approved_reviews').all() > > class ApprovedReviewsManager(models.Manager): > def get_queryset(self): > return super().get_queryset().filter(status=Review.APPROVED) > > class Review(models.Model): > NEW = 1 > APPROVED = 2 > STATUS_CHOICES = ( > (NEW, 'New'), > (APPROVED, 'Approved'), > ) > business = models.ForeignKey(Business) > text = models.CharField(max_length=255) > status = models.IntegerField(choices=STATUS_CHOICES, default=NEW) > > objects = models.Manager() > approved_reviews = ApprovedReviewsManager() > > class ApprovedReviewsTest(TestCase): > def test_with_prefetch(self): > business = Business() > business.save() > > review = Review() > review.business = business > review.save() > > businesses = > Business.objects.prefetch_related('review_set').all() > > business = businesses[0] > approved_reviews = > business.review_set(manager='approved_reviews').all() > > self.assertEqual(len(approved_reviews), 0) > }}} > > The full test project is available here: > https://github.com/mulka/django_prefetch_manager_bug/blob/master/review_site/tests.py New description: When using prefetch and specifying a custom manager to use for a reverse relation, Django doesn't filter correctly. Here's an example: {{{ class Business(models.Model): name = models.CharField(max_length=255) def approved_reviews(self): return self.review_set(manager='approved_reviews').all() class ApprovedReviewsManager(models.Manager): def get_queryset(self): return super().get_queryset().filter(status=Review.APPROVED) class Review(models.Model): NEW = 1 APPROVED = 2 STATUS_CHOICES = ( (NEW, 'New'), (APPROVED, 'Approved'), ) business = models.ForeignKey(Business) text = models.CharField(max_length=255) status = models.IntegerField(choices=STATUS_CHOICES, default=NEW) objects = models.Manager() approved_reviews = ApprovedReviewsManager() class ApprovedReviewsTest(TestCase): def test_with_prefetch(self): business = Business() business.save() review = Review() review.business = business review.save() businesses = Business.objects.prefetch_related('review_set').all() business = businesses[0] approved_reviews = business.review_set(manager='approved_reviews').all() self.assertEqual(len(approved_reviews), 0) }}} The full test project is available here: https://github.com/mulka/django_prefetch_manager_bug/blob/master/review_site/tests.py #This implementation: by Akshat verma class ToppingManager(models.Manager): def filter_vegetarian(self): return self.filter(is_vegetarian=True) #Looks non-standard. docs look like they do a safer method of modifying the super-class method for this sort of lazy-eval stuff. #If I rewrite your method in that style, it would look like: class ToppingManager(models.Manager): def filter_vegetarian(self): return super(ToppingManager, self).get_queryset().filter(is_vegetarian=True) #You wouldn't strictly need the super() here, but safer to use it because you should know that you want to start with the #models.Manager get_queryset method. -- Comment: #This implementation: by Akshat verma class ToppingManager(models.Manager): def filter_vegetarian(self): return self.filter(is_vegetarian=True) #Looks non-standard. docs look like they do a safer method of modifying the super-class method for this sort of lazy-eval stuff. #If I rewrite your method in that style, it would look like: class ToppingManager(models.Manager): def filter_vegetarian(self): return super(ToppingManager, self).get_queryset().filter(is_vegetarian=True) #You wouldn't strictly need the super() here, but safer to use it because you should know that you want to start with the #models.Manager get_queryset method. -- Ticket URL: <https://code.djangoproject.com/ticket/30355#comment:10> Django <https://code.djangoproject.com/> The Web framework for perfectionists with deadlines. -- You received this message because you are subscribed to the Google Groups "Django updates" group. To unsubscribe from this group and stop receiving emails from it, send an email to django-updates+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/django-updates/010701874695a99f-8f512c93-3107-4dbe-a9f8-abb7dc8ea9c9-000000%40eu-central-1.amazonses.com.