diff options
| -rw-r--r-- | tests/prefetch_related/tests.py | 24 |
1 files changed, 17 insertions, 7 deletions
diff --git a/tests/prefetch_related/tests.py b/tests/prefetch_related/tests.py index 5289661ad7..2f322482e3 100644 --- a/tests/prefetch_related/tests.py +++ b/tests/prefetch_related/tests.py @@ -1265,13 +1265,19 @@ class Ticket21760Tests(TestCase): self.assertNotIn(' JOIN ', str(queryset.query)) -class Ticket25546Tests(TestCase): +class DirectPrefechedObjectCacheReuseTests(TestCase): """ - Nested prefetch_related() shouldn't trigger duplicate queries for the same - lookup. + prefetch_related() reuses objects fetched in _prefetched_objects_cache. - Before, prefetch queries were for 'addresses', 'first_time_authors', and - 'first_time_authors__addresses'. The last query is the duplicate. + When objects are prefetched and not stored as an instance attribute (often + intermediary relationships), they are saved to the + _prefetched_objects_cache attribute. prefetch_related() takes + _prefetched_objects_cache into account when determining whether an object + has been fetched[1] and retrieves results from it when it is populated [2]. + + [1]: #25546 (duplicate queries on nested Prefetch) + [2]: #27554 (queryset evaluation fails with a mix of nested and flattened + prefetches) """ @classmethod @@ -1291,7 +1297,11 @@ class Ticket25546Tests(TestCase): AuthorAddress.objects.create(author=cls.author21, address='Happy place'), ] - def test_prefetch(self): + def test_detect_is_fetched(self): + """ + Nested prefetch_related() shouldn't trigger duplicate queries for the same + lookup. + """ with self.assertNumQueries(3): books = Book.objects.filter( title__in=['book1', 'book2'], @@ -1335,7 +1345,7 @@ class Ticket25546Tests(TestCase): list(book2.first_time_authors.all()[0].addresses.all().all()) ) - def test_prefetch_with_to_attr(self): + def test_detect_is_fetched_with_to_attr(self): with self.assertNumQueries(3): books = Book.objects.filter( title__in=['book1', 'book2'], |