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Fixed #26916 -- Fixed prefetch_related when using a cached_property as to_attr.

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Thanks Trac alias karyon for the report and Tim for the review.
This commit is contained in:
Simon Charette 2016-07-19 14:55:59 -04:00
parent 081fdaf110
commit 271bfe65d9
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3 changed files with 23 additions and 2 deletions
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9
django/db/models/query.py
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@ -25,7 +25,7 @@ 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.functional import cached_property, partition
from django.utils.version import get_version
# The maximum number of items to display in a QuerySet.__repr__
@ -1545,7 +1545,12 @@ def get_prefetcher(instance, through_attr, to_attr):
if hasattr(rel_obj, 'get_prefetch_queryset'):
prefetcher = rel_obj
if through_attr != to_attr:
is_fetched = hasattr(instance, to_attr)
# Special case cached_property instances because hasattr
# triggers attribute computation and assignment.
if isinstance(getattr(instance.__class__, to_attr, None), cached_property):
is_fetched = to_attr in instance.__dict__
else:
is_fetched = hasattr(instance, to_attr)
else:
is_fetched = through_attr in instance._prefetched_objects_cache
return prefetcher, rel_obj_descriptor, attr_found, is_fetched