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Code Issues 25 Releases Wiki Activity

Fixed #30493 -- Fixed prefetch_related() for GenericRelation with different content types.

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Co-Authored-By: Mariusz Felisiak <felisiak.mariusz@gmail.com>

Thanks Simon Charette for the review.
This commit is contained in:
can 2019-05-29 20:24:37 +03:00 committed by Mariusz Felisiak
parent f66021f3f7
commit dffa3e1992
2 changed files with 38 additions and 9 deletions
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29
django/contrib/contenttypes/fields.py
View File

@ -1,4 +1,6 @@
import functools
import itertools
import operator
from collections import defaultdict
from django.contrib.contenttypes.models import ContentType
@ -566,19 +568,28 @@ def create_generic_related_manager(superclass, rel):
queryset._add_hints(instance=instances[0])
queryset = queryset.using(queryset._db or self._db)
query = {
'%s__pk' % self.content_type_field_name: self.content_type.id,
'%s__in' % self.object_id_field_name: {obj.pk for obj in instances}
}
# Group instances by content types.
content_type_queries = (
models.Q(**{
'%s__pk' % self.content_type_field_name: content_type_id,
'%s__in' % self.object_id_field_name: {obj.pk for obj in objs}
})
for content_type_id, objs in itertools.groupby(
sorted(instances, key=lambda obj: self.get_content_type(obj).pk),
lambda obj: self.get_content_type(obj).pk,
)
)
query = functools.reduce(operator.or_, content_type_queries)
# We (possibly) need to convert object IDs to the type of the
# instances' PK in order to match up instances:
object_id_converter = instances[0]._meta.pk.to_python
return (
queryset.filter(**query),
lambda relobj: object_id_converter(getattr(relobj, self.object_id_field_name)),
lambda obj: obj.pk,
queryset.filter(query),
lambda relobj: (
object_id_converter(getattr(relobj, self.object_id_field_name)),
relobj.content_type_id
),
lambda obj: (obj.pk, self.get_content_type(obj).pk),
False,
self.prefetch_cache_name,
False,

18
tests/generic_relations/tests.py
View File

@ -546,6 +546,24 @@ class GenericRelationsTests(TestCase):
platypus.tags.remove(weird_tag)
self.assertSequenceEqual(platypus.tags.all(), [furry_tag])
def test_prefetch_related_different_content_types(self):
TaggedItem.objects.create(content_object=self.platypus, tag='prefetch_tag_1')
TaggedItem.objects.create(
content_object=Vegetable.objects.create(name='Broccoli'),
tag='prefetch_tag_2',
)
TaggedItem.objects.create(
content_object=Animal.objects.create(common_name='Bear'),
tag='prefetch_tag_3',
)
qs = TaggedItem.objects.filter(
tag__startswith='prefetch_tag_',
).prefetch_related('content_object', 'content_object__tags')
with self.assertNumQueries(4):
tags = list(qs)
for tag in tags:
self.assertSequenceEqual(tag.content_object.tags.all(), [tag])
class ProxyRelatedModelTest(TestCase):
def test_default_behavior(self):