source/django
1
0
Fork 0
mirror of https://github.com/django/django.git synced 2026-02-09 02:49:25 +08:00
Code Issues Packages Projects Releases Wiki Activity

Fixed #35442 -- Prevented N+1 queries in RelatedManager with only().

Browse Source 
Co-authored-by: Simon Charette <charette.s@gmail.com>
This commit is contained in:
Samriddha9619
2026-01-05 11:18:40 +05:30
committed by Jacob Walls
parent 73c5e94521
commit 040bb3eba7
2 changed files with 26 additions and 14 deletions
Download Patch File Download Diff File Expand all files Collapse all files

25
django/db/models/query.py
View File

@@ -114,16 +114,15 @@ class ModelIterable(BaseIterable):
(
field,
related_objs,
operator.attrgetter(
*[
(
field.attname
if from_field == "self"
else queryset.model._meta.get_field(from_field).attname
)
for from_field in field.from_fields
]
),
attnames := [
(
field.attname
if from_field == "self"
else queryset.model._meta.get_field(from_field).attname
)
for from_field in field.from_fields
],
operator.attrgetter(*attnames),
)
for field, related_objs in queryset._known_related_objects.items()
]
@@ -145,10 +144,14 @@ class ModelIterable(BaseIterable):
setattr(obj, attr_name, row[col_pos])
# Add the known related objects to the model.
for field, rel_objs, rel_getter in known_related_objects:
for field, rel_objs, rel_attnames, rel_getter in known_related_objects:
# Avoid overwriting objects loaded by, e.g., select_related().
if field.is_cached(obj):
continue
# Avoid fetching potentially deferred attributes that would
# result in unexpected queries.
if any(attname not in obj.__dict__ for attname in rel_attnames):
continue
rel_obj_id = rel_getter(obj)
try:
rel_obj = rel_objs[rel_obj_id]

15
tests/defer/tests.py
View File

@@ -49,9 +49,9 @@ class DeferTests(AssertionMixin, TestCase):
# of them except the model's primary key see #15494
self.assert_delayed(qs.only("pk")[0], 3)
# You can use 'pk' with reverse foreign key lookups.
# The related_id is always set even if it's not fetched from the DB,
# so pk and related_id are not deferred.
self.assert_delayed(self.s1.primary_set.only("pk")[0], 2)
# The related_id is not set if it's not fetched from the DB,
# so pk is not deferred, but related_id is.
self.assert_delayed(self.s1.primary_set.only("pk")[0], 3)
def test_defer_only_chaining(self):
qs = Primary.objects.all()
@@ -84,6 +84,15 @@ class DeferTests(AssertionMixin, TestCase):
with self.assertRaisesMessage(TypeError, msg):
Primary.objects.only(None)
def test_only_related_manager_optimization(self):
s = Secondary.objects.create(first="one", second="two")
Primary.objects.bulk_create(
[Primary(name="p1", value="v1", related=s) for _ in range(5)]
)
with self.assertNumQueries(1):
for p in s.primary_set.only("pk"):
_ = p.pk
def test_defer_extra(self):
qs = Primary.objects.all()
self.assert_delayed(qs.defer("name").extra(select={"a": 1})[0], 1)