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Fixed #26226 -- Made related managers honor the queryset used for prefetching their results. 

Thanks Loïc for the suggested improvements and Tim for the review.
This commit is contained in:
Simon Charette 2016-02-18 22:37:11 -05:00
parent 5d240b070d
commit c92123cc1d
6 changed files with 133 additions and 22 deletions
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11
django/contrib/contenttypes/fields.py
View File

@ -521,12 +521,19 @@ def create_generic_related_manager(superclass, rel):
def __str__(self):
return repr(self)
def _apply_rel_filters(self, queryset):
"""
Filter the queryset for the instance this manager is bound to.
"""
db = self._db or router.db_for_read(self.model, instance=self.instance)
return queryset.using(db).filter(**self.core_filters)
def get_queryset(self):
try:
return self.instance._prefetched_objects_cache[self.prefetch_cache_name]
except (AttributeError, KeyError):
db = self._db or router.db_for_read(self.model, instance=self.instance)
return super(GenericRelatedObjectManager, self).get_queryset().using(db).filter(**self.core_filters)
queryset = super(GenericRelatedObjectManager, self).get_queryset()
return self._apply_rel_filters(queryset)
def get_prefetch_queryset(self, instances, queryset=None):
if queryset is None:

48
django/db/models/fields/related_descriptors.py
View File

@ -502,23 +502,29 @@ def create_reverse_many_to_one_manager(superclass, rel):
return manager_class(self.instance)
do_not_call_in_templates = True
def _apply_rel_filters(self, queryset):
"""
Filter the queryset for the instance this manager is bound to.
"""
db = self._db or router.db_for_read(self.model, instance=self.instance)
empty_strings_as_null = connections[db].features.interprets_empty_strings_as_nulls
queryset._add_hints(instance=self.instance)
if self._db:
queryset = queryset.using(self._db)
queryset = queryset.filter(**self.core_filters)
for field in self.field.foreign_related_fields:
val = getattr(self.instance, field.attname)
if val is None or (val == '' and empty_strings_as_null):
return queryset.none()
queryset._known_related_objects = {self.field: {self.instance.pk: self.instance}}
return queryset
def get_queryset(self):
try:
return self.instance._prefetched_objects_cache[self.field.related_query_name()]
except (AttributeError, KeyError):
db = self._db or router.db_for_read(self.model, instance=self.instance)
empty_strings_as_null = connections[db].features.interprets_empty_strings_as_nulls
qs = super(RelatedManager, self).get_queryset()
qs._add_hints(instance=self.instance)
if self._db:
qs = qs.using(self._db)
qs = qs.filter(**self.core_filters)
for field in self.field.foreign_related_fields:
val = getattr(self.instance, field.attname)
if val is None or (val == '' and empty_strings_as_null):
return qs.none()
qs._known_related_objects = {self.field: {self.instance.pk: self.instance}}
return qs
queryset = super(RelatedManager, self).get_queryset()
return self._apply_rel_filters(queryset)
def get_prefetch_queryset(self, instances, queryset=None):
if queryset is None:
@ -776,15 +782,21 @@ def create_forward_many_to_many_manager(superclass, rel, reverse):
filters |= symmetrical_filters
return filters
def _apply_rel_filters(self, queryset):
"""
Filter the queryset for the instance this manager is bound to.
"""
queryset._add_hints(instance=self.instance)
if self._db:
queryset = queryset.using(self._db)
return queryset._next_is_sticky().filter(**self.core_filters)
def get_queryset(self):
try:
return self.instance._prefetched_objects_cache[self.prefetch_cache_name]
except (AttributeError, KeyError):
qs = super(ManyRelatedManager, self).get_queryset()
qs._add_hints(instance=self.instance)
if self._db:
qs = qs.using(self._db)
return qs._next_is_sticky().filter(**self.core_filters)
queryset = super(ManyRelatedManager, self).get_queryset()
return self._apply_rel_filters(queryset)
def get_prefetch_queryset(self, instances, queryset=None):
if queryset is None:

23
django/db/models/query.py
View File

@ -23,6 +23,7 @@ from django.db.models.query_utils import (
)
from django.db.models.sql.constants import CURSOR
from django.utils import six, timezone
from django.utils.deprecation import RemovedInDjango20Warning
from django.utils.functional import partition
from django.utils.version import get_version
@ -1608,6 +1609,9 @@ def prefetch_one_level(instances, prefetcher, lookup, level):
msg = 'to_attr={} conflicts with a field on the {} model.'
raise ValueError(msg.format(to_attr, model.__name__))
# Whether or not we're prefetching the last part of the lookup.
leaf = len(lookup.prefetch_through.split(LOOKUP_SEP)) - 1 == level
for obj in instances:
instance_attr_val = instance_attr(obj)
vals = rel_obj_cache.get(instance_attr_val, [])
@ -1621,8 +1625,23 @@ def prefetch_one_level(instances, prefetcher, lookup, level):
setattr(obj, to_attr, vals)
obj._prefetched_objects_cache[cache_name] = vals
else:
# Cache in the QuerySet.all().
qs = getattr(obj, to_attr).all()
manager = getattr(obj, to_attr)
if leaf and lookup.queryset is not None:
try:
apply_rel_filter = manager._apply_rel_filters
except AttributeError:
warnings.warn(
"The `%s.%s` class must implement a `_apply_rel_filters()` "
"method that accepts a `QuerySet` as its single "
"argument and returns an appropriately filtered version "
"of it." % (manager.__class__.__module__, manager.__class__.__name__),
RemovedInDjango20Warning,
)
qs = manager.get_queryset()
else:
qs = apply_rel_filter(lookup.queryset)
else:
qs = manager.get_queryset()
qs._result_cache = vals
# We don't want the individual qs doing prefetch_related now,
# since we have merged this into the current work.

3
docs/internals/deprecation.txt
View File

@ -144,6 +144,9 @@ details on these changes.
* The ``__search`` query lookup and the
``DatabaseOperations.fulltext_search_sql()`` method will be removed.
* The shim for supporting custom related manager classes without a
``_apply_rel_filters()`` method will be removed.
.. _deprecation-removed-in-1.10:
1.10

11
docs/releases/1.10.txt
View File

@ -762,6 +762,17 @@ features, is deprecated. Replace it with a custom lookup::
models.CharField.register_lookup(Search)
models.TextField.register_lookup(Search)
Custom manager classes available through ``prefetch_related`` must define a ``_apply_rel_filters()`` method
-----------------------------------------------------------------------------------------------------------
If you defined a custom manager class available through
:meth:`~django.db.models.query.QuerySet.prefetch_related` you must make sure
it defines a ``_apply_rel_filters()`` method.
This method must accept a :class:`~django.db.models.query.QuerySet` instance
as its single argument and return a filtered version of the queryset for the
model instance the manager is bound to.
Miscellaneous
-------------

59
tests/prefetch_related/tests.py
View File

@ -1,5 +1,7 @@
from __future__ import unicode_literals
import warnings
from django.contrib.contenttypes.models import ContentType
from django.core.exceptions import ObjectDoesNotExist
from django.db import connection
@ -693,6 +695,16 @@ class CustomPrefetchTests(TestCase):
).first()
self.assertIsNone(room.main_room_of_attr)
# The custom queryset filters should be applied to the queryset
# instance returned by the manager.
person = Person.objects.prefetch_related(
Prefetch('houses', queryset=House.objects.filter(name='House 1')),
).get(pk=self.person1.pk)
self.assertEqual(
list(person.houses.all()),
list(person.houses.all().all()),
)
def test_nested_prefetch_related_are_not_overwritten(self):
# Regression test for #24873
houses_2 = House.objects.prefetch_related(Prefetch('rooms'))
@ -704,6 +716,30 @@ class CustomPrefetchTests(TestCase):
self.room2_1
)
def test_apply_rel_filters_deprecation_shim(self):
# Simulate a missing `_apply_rel_filters` method.
del Person.houses.related_manager_cls._apply_rel_filters
# Also remove `get_queryset` as it rely on `_apply_rel_filters`.
del Person.houses.related_manager_cls.get_queryset
try:
with warnings.catch_warnings(record=True) as warns:
warnings.simplefilter('always')
list(Person.objects.prefetch_related(
Prefetch('houses', queryset=House.objects.filter(name='House 1'))
))
finally:
# Deleting `related_manager_cls` will force the creation of a new
# class since it's a `cached_property`.
del Person.houses.related_manager_cls
msg = (
'The `django.db.models.fields.related_descriptors.ManyRelatedManager` class '
'must implement a `_apply_rel_filters()` method that accepts a `QuerySet` as '
'its single argument and returns an appropriately filtered version of it.'
)
self.assertEqual(len(warns), 2) # Once person.
self.assertEqual(str(warns[0].message), msg)
self.assertEqual(str(warns[0].message), msg)
class DefaultManagerTests(TestCase):
@ -849,6 +885,10 @@ class GenericRelationTests(TestCase):
with self.assertNumQueries(0):
self.assertEqual(list(bookmark.tags.all()), [django_tag])
# The custom queryset filters should be applied to the queryset
# instance returned by the manager.
self.assertEqual(list(bookmark.tags.all()), list(bookmark.tags.all().all()))
class MultiTableInheritanceTest(TestCase):
@ -1296,6 +1336,25 @@ class Ticket25546Tests(TestCase):
self.assertListEqual(list(book1.first_time_authors.all()[1].addresses.all()), [])
self.assertListEqual(list(book2.first_time_authors.all()[0].addresses.all()), [self.author2_address1])
self.assertEqual(
list(book1.first_time_authors.all()), list(book1.first_time_authors.all().all())
)
self.assertEqual(
list(book2.first_time_authors.all()), list(book2.first_time_authors.all().all())
)
self.assertEqual(
list(book1.first_time_authors.all()[0].addresses.all()),
list(book1.first_time_authors.all()[0].addresses.all().all())
)
self.assertEqual(
list(book1.first_time_authors.all()[1].addresses.all()),
list(book1.first_time_authors.all()[1].addresses.all().all())
)
self.assertEqual(
list(book2.first_time_authors.all()[0].addresses.all()),
list(book2.first_time_authors.all()[0].addresses.all().all())
)
def test_prefetch_with_to_attr(self):
with self.assertNumQueries(3):
books = Book.objects.filter(