Opened 9 years ago
Closed 9 years ago
#24873 closed Bug (fixed)
Error while using Prefech on more than two levels
Reported by: | Gagaro | Owned by: | Gagaro |
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Component: | Database layer (models, ORM) | Version: | dev |
Severity: | Normal | Keywords: | Prefetch prefetch_related |
Cc: | Triage Stage: | Ready for checkin | |
Has patch: | yes | Needs documentation: | no |
Needs tests: | no | Patch needs improvement: | no |
Easy pickings: | no | UI/UX: | no |
Description (last modified by )
Given the following models:
# Foreign Keys class A(models.Model): pass class B(models.Model): a = models.ForeignKey(A, related_name='b') class C(models.Model): b = models.ForeignKey(B, related_name='c') class D(models.Model): c = models.ForeignKey(C, related_name='d') #ManyToMany Fields class E(models.Model): pass class F(models.Model): e = models.ManyToManyField(E, related_name='f') class G(models.Model): f = models.ManyToManyField(F, related_name='g') class H(models.Model): g = models.ManyToManyField(G, related_name='h')
And the following tests:
class PrefetchForeignKeyTest(TestCase): def setUp(self): a = A.objects.create() b = B.objects.create(a=a) c = C.objects.create(b=b) D.objects.create(c=c) def test_with_prefetch(self): c = C.objects.prefetch_related(Prefetch('d')) b = B.objects.prefetch_related(Prefetch('c', queryset=c)) a = A.objects.prefetch_related(Prefetch('b', queryset=b)) list(a) a.first().b.first().c.first().d.first() def test_without_prefetch(self): c = C.objects.prefetch_related('d') b = B.objects.prefetch_related(Prefetch('c', queryset=c)) a = A.objects.prefetch_related(Prefetch('b', queryset=b)) list(a) a.first().b.first().c.first().d.first() class PrefetchManyTest(TestCase): def setUp(self): e = E.objects.create() f = F.objects.create() g = G.objects.create() h = H.objects.create() f.e.add(e) g.f.add(f) h.g.add(g) def test_with_prefetch(self): g = G.objects.prefetch_related(Prefetch('h')) f = F.objects.prefetch_related(Prefetch('g', queryset=g)) e = E.objects.prefetch_related(Prefetch('f', queryset=f)) list(e) e.first().f.first().g.first().h.first() def test_without_prefetch(self): g = G.objects.prefetch_related('h') f = F.objects.prefetch_related(Prefetch('g', queryset=g)) e = E.objects.prefetch_related(Prefetch('f', queryset=f)) list(e) e.first().f.first().g.first().h.first()
The tests will fail. The backtrace with master is:
====================================================================== ERROR: test_with_prefetch (models_test.tests.PrefetchManyTest) ---------------------------------------------------------------------- Traceback (most recent call last): File "/home/gagaro/django/modules/test/django_test/models_test/tests.py", line 49, in test_with_prefetch e.first().f.first().g.first().h.first() File "/home/gagaro/.virtualenvs/django-test/local/lib/python2.7/site-packages/django/db/models/query.py", line 543, in first objects = list((self if self.ordered else self.order_by('pk'))[:1]) File "/home/gagaro/.virtualenvs/django-test/local/lib/python2.7/site-packages/django/db/models/query.py", line 258, in __iter__ self._fetch_all() File "/home/gagaro/.virtualenvs/django-test/local/lib/python2.7/site-packages/django/db/models/query.py", line 1065, in _fetch_all self._prefetch_related_objects() File "/home/gagaro/.virtualenvs/django-test/local/lib/python2.7/site-packages/django/db/models/query.py", line 649, in _prefetch_related_objects prefetch_related_objects(self._result_cache, self._prefetch_related_lookups) File "/home/gagaro/.virtualenvs/django-test/local/lib/python2.7/site-packages/django/db/models/query.py", line 1426, in prefetch_related_objects (through_attr, first_obj.__class__.__name__, lookup.prefetch_through)) AttributeError: Cannot find 'f' on F object, 'f__f__g' is an invalid parameter to prefetch_related() ====================================================================== ERROR: test_without_prefetch (models_test.tests.PrefetchManyTest) ---------------------------------------------------------------------- Traceback (most recent call last): File "/home/gagaro/django/modules/test/django_test/models_test/tests.py", line 56, in test_without_prefetch e.first().f.first().g.first().h.first() File "/home/gagaro/.virtualenvs/django-test/local/lib/python2.7/site-packages/django/db/models/query.py", line 543, in first objects = list((self if self.ordered else self.order_by('pk'))[:1]) File "/home/gagaro/.virtualenvs/django-test/local/lib/python2.7/site-packages/django/db/models/query.py", line 258, in __iter__ self._fetch_all() File "/home/gagaro/.virtualenvs/django-test/local/lib/python2.7/site-packages/django/db/models/query.py", line 1065, in _fetch_all self._prefetch_related_objects() File "/home/gagaro/.virtualenvs/django-test/local/lib/python2.7/site-packages/django/db/models/query.py", line 649, in _prefetch_related_objects prefetch_related_objects(self._result_cache, self._prefetch_related_lookups) File "/home/gagaro/.virtualenvs/django-test/local/lib/python2.7/site-packages/django/db/models/query.py", line 1426, in prefetch_related_objects (through_attr, first_obj.__class__.__name__, lookup.prefetch_through)) AttributeError: Cannot find 'f' on F object, 'f__f__g' is an invalid parameter to prefetch_related() ====================================================================== ERROR: test_with_prefetch (models_test.tests.PrefetchForeignKeyTest) ---------------------------------------------------------------------- Traceback (most recent call last): File "/home/gagaro/django/modules/test/django_test/models_test/tests.py", line 23, in test_with_prefetch list(a) File "/home/gagaro/.virtualenvs/django-test/local/lib/python2.7/site-packages/django/db/models/query.py", line 258, in __iter__ self._fetch_all() File "/home/gagaro/.virtualenvs/django-test/local/lib/python2.7/site-packages/django/db/models/query.py", line 1065, in _fetch_all self._prefetch_related_objects() File "/home/gagaro/.virtualenvs/django-test/local/lib/python2.7/site-packages/django/db/models/query.py", line 649, in _prefetch_related_objects prefetch_related_objects(self._result_cache, self._prefetch_related_lookups) File "/home/gagaro/.virtualenvs/django-test/local/lib/python2.7/site-packages/django/db/models/query.py", line 1437, in prefetch_related_objects obj_list, additional_lookups = prefetch_one_level(obj_list, prefetcher, lookup, level) File "/home/gagaro/.virtualenvs/django-test/local/lib/python2.7/site-packages/django/db/models/query.py", line 1536, in prefetch_one_level prefetcher.get_prefetch_queryset(instances, lookup.get_current_queryset(level))) File "/home/gagaro/.virtualenvs/django-test/local/lib/python2.7/site-packages/django/db/models/fields/related.py", line 753, in get_prefetch_queryset for rel_obj in queryset: File "/home/gagaro/.virtualenvs/django-test/local/lib/python2.7/site-packages/django/db/models/query.py", line 258, in __iter__ self._fetch_all() File "/home/gagaro/.virtualenvs/django-test/local/lib/python2.7/site-packages/django/db/models/query.py", line 1065, in _fetch_all self._prefetch_related_objects() File "/home/gagaro/.virtualenvs/django-test/local/lib/python2.7/site-packages/django/db/models/query.py", line 649, in _prefetch_related_objects prefetch_related_objects(self._result_cache, self._prefetch_related_lookups) File "/home/gagaro/.virtualenvs/django-test/local/lib/python2.7/site-packages/django/db/models/query.py", line 1426, in prefetch_related_objects (through_attr, first_obj.__class__.__name__, lookup.prefetch_through)) AttributeError: Cannot find 'c' on C object, 'c__d' is an invalid parameter to prefetch_related() ====================================================================== ERROR: test_without_prefetch (models_test.tests.PrefetchForeignKeyTest) ---------------------------------------------------------------------- Traceback (most recent call last): File "/home/gagaro/django/modules/test/django_test/models_test/tests.py", line 31, in test_without_prefetch a.first().b.first().c.first().d.first() File "/home/gagaro/.virtualenvs/django-test/local/lib/python2.7/site-packages/django/db/models/query.py", line 543, in first objects = list((self if self.ordered else self.order_by('pk'))[:1]) File "/home/gagaro/.virtualenvs/django-test/local/lib/python2.7/site-packages/django/db/models/query.py", line 258, in __iter__ self._fetch_all() File "/home/gagaro/.virtualenvs/django-test/local/lib/python2.7/site-packages/django/db/models/query.py", line 1065, in _fetch_all self._prefetch_related_objects() File "/home/gagaro/.virtualenvs/django-test/local/lib/python2.7/site-packages/django/db/models/query.py", line 649, in _prefetch_related_objects prefetch_related_objects(self._result_cache, self._prefetch_related_lookups) File "/home/gagaro/.virtualenvs/django-test/local/lib/python2.7/site-packages/django/db/models/query.py", line 1437, in prefetch_related_objects obj_list, additional_lookups = prefetch_one_level(obj_list, prefetcher, lookup, level) File "/home/gagaro/.virtualenvs/django-test/local/lib/python2.7/site-packages/django/db/models/query.py", line 1536, in prefetch_one_level prefetcher.get_prefetch_queryset(instances, lookup.get_current_queryset(level))) File "/home/gagaro/.virtualenvs/django-test/local/lib/python2.7/site-packages/django/db/models/fields/related.py", line 753, in get_prefetch_queryset for rel_obj in queryset: File "/home/gagaro/.virtualenvs/django-test/local/lib/python2.7/site-packages/django/db/models/query.py", line 258, in __iter__ self._fetch_all() File "/home/gagaro/.virtualenvs/django-test/local/lib/python2.7/site-packages/django/db/models/query.py", line 1065, in _fetch_all self._prefetch_related_objects() File "/home/gagaro/.virtualenvs/django-test/local/lib/python2.7/site-packages/django/db/models/query.py", line 649, in _prefetch_related_objects prefetch_related_objects(self._result_cache, self._prefetch_related_lookups) File "/home/gagaro/.virtualenvs/django-test/local/lib/python2.7/site-packages/django/db/models/query.py", line 1426, in prefetch_related_objects (through_attr, first_obj.__class__.__name__, lookup.prefetch_through)) AttributeError: Cannot find 'b' on B object, 'b__c' is an invalid parameter to prefetch_related()
I tested with Django 1.7, 1.8, 1.8.2 and master (commit 24718b7dccd64dfa118fe8136e7b175babec679b).
Change History (8)
comment:1 by , 9 years ago
Triage Stage: | Unreviewed → Accepted |
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comment:2 by , 9 years ago
Description: | modified (diff) |
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comment:3 by , 9 years ago
I did some more testing. All the tests actually fail when I try to access the objects. I also added tests with m2m (which only fail when the objects are accessed).
comment:4 by , 9 years ago
I found and corrected the bug. I'm working on the pull request (it may take a little bit of time as it is my first and I still need to add regression tests).
comment:5 by , 9 years ago
Owner: | changed from | to
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Status: | new → assigned |
comment:7 by , 9 years ago
Has patch: | set |
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Triage Stage: | Accepted → Ready for checkin |
Would be nice for someone familiar with the prefetch stuff to double check this.
I don't have much experience with
prefetch_related()
but as far as I understand, the two tests should work identically.