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Fixed #17485 -- Made defer work with select_related

This commit tackles a couple of issues. First, in certain cases there
were some mixups if field.attname or field.name should be deferred.
Field.attname is now always used.

Another issue tackled is a case where field is both deferred by
.only(), and selected by select_related. This case is now an error.

A lot of thanks to koniiiik (Michal Petrucha) for the patch, and
to Andrei Antoukh for review.
  • Loading branch information...
commit b6c356b7bb97f3d6d4831b31e67868313bbbc090 1 parent 5318783
@akaariai akaariai authored
View
7 django/db/models/query.py
@@ -1296,7 +1296,7 @@ def get_klass_info(klass, max_depth=0, cur_depth=0, requested=None,
# Build the list of fields that *haven't* been requested
for field, model in klass._meta.get_fields_with_model():
if field.name not in load_fields:
- skip.add(field.name)
+ skip.add(field.attname)
elif local_only and model is not None:
continue
else:
@@ -1327,7 +1327,7 @@ def get_klass_info(klass, max_depth=0, cur_depth=0, requested=None,
related_fields = []
for f in klass._meta.fields:
- if select_related_descend(f, restricted, requested):
+ if select_related_descend(f, restricted, requested, load_fields):
if restricted:
next = requested[f.name]
else:
@@ -1339,7 +1339,8 @@ def get_klass_info(klass, max_depth=0, cur_depth=0, requested=None,
reverse_related_fields = []
if restricted:
for o in klass._meta.get_all_related_objects():
- if o.field.unique and select_related_descend(o.field, restricted, requested, reverse=True):
+ if o.field.unique and select_related_descend(o.field, restricted, requested,
+ only_load.get(o.model), reverse=True):
next = requested[o.field.related_query_name()]
klass_info = get_klass_info(o.model, max_depth=max_depth, cur_depth=cur_depth+1,
requested=next, only_load=only_load, local_only=True)
View
13 django/db/models/query_utils.py
@@ -126,18 +126,19 @@ def _check_parent_chain(self, instance, name):
return None
-def select_related_descend(field, restricted, requested, reverse=False):
+def select_related_descend(field, restricted, requested, load_fields, reverse=False):
"""
Returns True if this field should be used to descend deeper for
select_related() purposes. Used by both the query construction code
(sql.query.fill_related_selections()) and the model instance creation code
- (query.get_cached_row()).
+ (query.get_klass_info()).
Arguments:
* field - the field to be checked
* restricted - a boolean field, indicating if the field list has been
manually restricted using a requested clause)
* requested - The select_related() dictionary.
+ * load_fields - the set of fields to be loaded on this model
* reverse - boolean, True if we are checking a reverse select related
"""
if not field.rel:
@@ -151,6 +152,14 @@ def select_related_descend(field, restricted, requested, reverse=False):
return False
if not restricted and field.null:
return False
+ if load_fields:
+ if field.name not in load_fields:
+ if restricted and field.name in requested:
+ raise InvalidQuery("Field %s.%s cannot be both deferred"
+ " and traversed using select_related"
+ " at the same time." %
+ (field.model._meta.object_name, field.name))
+ return False
return True
# This function is needed because data descriptors must be defined on a class
View
7 django/db/models/sql/compiler.py
@@ -596,6 +596,7 @@ def fill_related_selections(self, opts=None, root_alias=None, cur_depth=1,
if avoid_set is None:
avoid_set = set()
orig_dupe_set = dupe_set
+ only_load = self.query.get_loaded_field_names()
# Setup for the case when only particular related fields should be
# included in the related selection.
@@ -607,7 +608,8 @@ def fill_related_selections(self, opts=None, root_alias=None, cur_depth=1,
restricted = False
for f, model in opts.get_fields_with_model():
- if not select_related_descend(f, restricted, requested):
+ if not select_related_descend(f, restricted, requested,
+ only_load.get(model or self.query.model)):
continue
# The "avoid" set is aliases we want to avoid just for this
# particular branch of the recursion. They aren't permanently
@@ -680,7 +682,8 @@ def fill_related_selections(self, opts=None, root_alias=None, cur_depth=1,
if o.field.unique
]
for f, model in related_fields:
- if not select_related_descend(f, restricted, requested, reverse=True):
+ if not select_related_descend(f, restricted, requested,
+ only_load.get(model), reverse=True):
continue
# The "avoid" set is aliases we want to avoid just for this
# particular branch of the recursion. They aren't permanently
View
12 django/db/models/sql/query.py
@@ -1845,9 +1845,15 @@ def get_loaded_field_names(self):
If no fields are marked for deferral, returns an empty dictionary.
"""
- collection = {}
- self.deferred_to_data(collection, self.get_loaded_field_names_cb)
- return collection
+ # We cache this because we call this function multiple times
+ # (compiler.fill_related_selections, query.iterator)
+ try:
+ return self._loaded_field_names_cache
+ except AttributeError:
+ collection = {}
+ self.deferred_to_data(collection, self.get_loaded_field_names_cb)
+ self._loaded_field_names_cache = collection
+ return collection
def get_loaded_field_names_cb(self, target, model, fields):
"""
View
11 docs/ref/models/querysets.txt
@@ -1081,11 +1081,13 @@ to ``defer()``::
# Load all fields immediately.
my_queryset.defer(None)
+.. versionchanged:: 1.5
+
Some fields in a model won't be deferred, even if you ask for them. You can
never defer the loading of the primary key. If you are using
:meth:`select_related()` to retrieve related models, you shouldn't defer the
-loading of the field that connects from the primary model to the related one
-(at the moment, that doesn't raise an error, but it will eventually).
+loading of the field that connects from the primary model to the related
+one, doing so will result in an error.
.. note::
@@ -1145,9 +1147,12 @@ logically::
# existing set of fields).
Entry.objects.defer("body").only("headline", "body")
+.. versionchanged:: 1.5
+
All of the cautions in the note for the :meth:`defer` documentation apply to
``only()`` as well. Use it cautiously and only after exhausting your other
-options.
+options. Also note that using :meth:`only` and omitting a field requested
+using :meth:`select_related` is an error as well.
using
~~~~~
View
20 tests/modeltests/defer/tests.py
@@ -1,6 +1,6 @@
from __future__ import absolute_import
-from django.db.models.query_utils import DeferredAttribute
+from django.db.models.query_utils import DeferredAttribute, InvalidQuery
from django.test import TestCase
from .models import Secondary, Primary, Child, BigChild, ChildProxy
@@ -73,9 +73,19 @@ def test_defer(self):
self.assert_delayed(qs.defer("name").get(pk=p1.pk), 1)
self.assert_delayed(qs.only("name").get(pk=p1.pk), 2)
- # DOES THIS WORK?
- self.assert_delayed(qs.only("name").select_related("related")[0], 1)
- self.assert_delayed(qs.defer("related").select_related("related")[0], 0)
+ # When we defer a field and also select_related it, the query is
+ # invalid and raises an exception.
+ with self.assertRaises(InvalidQuery):
+ qs.only("name").select_related("related")[0]
+ with self.assertRaises(InvalidQuery):
+ qs.defer("related").select_related("related")[0]
+
+ # With a depth-based select_related, all deferred ForeignKeys are
+ # deferred instead of traversed.
+ with self.assertNumQueries(3):
+ obj = qs.defer("related").select_related()[0]
+ self.assert_delayed(obj, 1)
+ self.assertEqual(obj.related.id, s1.pk)
# Saving models with deferred fields is possible (but inefficient,
# since every field has to be retrieved first).
@@ -155,7 +165,7 @@ def test_defer_proxy(self):
children = ChildProxy.objects.all().select_related().only('id', 'name')
self.assertEqual(len(children), 1)
child = children[0]
- self.assert_delayed(child, 1)
+ self.assert_delayed(child, 2)
self.assertEqual(child.name, 'p1')
self.assertEqual(child.value, 'xx')
View
4 tests/regressiontests/defer_regress/models.py
@@ -47,3 +47,7 @@ def __unicode__(self):
class Feature(models.Model):
item = models.ForeignKey(SimpleItem)
+
+class ItemAndSimpleItem(models.Model):
+ item = models.ForeignKey(Item)
+ simple = models.ForeignKey(SimpleItem)
View
26 tests/regressiontests/defer_regress/tests.py
@@ -9,7 +9,7 @@
from django.test import TestCase
from .models import (ResolveThis, Item, RelatedItem, Child, Leaf, Proxy,
- SimpleItem, Feature)
+ SimpleItem, Feature, ItemAndSimpleItem)
class DeferRegressionTest(TestCase):
@@ -109,6 +109,7 @@ def test_basic(self):
Child,
Feature,
Item,
+ ItemAndSimpleItem,
Leaf,
Proxy,
RelatedItem,
@@ -125,12 +126,16 @@ def test_basic(self):
),
)
)
+ # FIXME: This is dependent on the order in which tests are run --
+ # this test case has to be the first, otherwise a LOT more classes
+ # appear.
self.assertEqual(
klasses, [
"Child",
"Child_Deferred_value",
"Feature",
"Item",
+ "ItemAndSimpleItem",
"Item_Deferred_name",
"Item_Deferred_name_other_value_text",
"Item_Deferred_name_other_value_value",
@@ -139,7 +144,7 @@ def test_basic(self):
"Leaf",
"Leaf_Deferred_child_id_second_child_id_value",
"Leaf_Deferred_name_value",
- "Leaf_Deferred_second_child_value",
+ "Leaf_Deferred_second_child_id_value",
"Leaf_Deferred_value",
"Proxy",
"RelatedItem",
@@ -175,6 +180,23 @@ def test_resolve_columns(self):
self.assertEqual(1, qs.count())
self.assertEqual('Foobar', qs[0].name)
+ def test_defer_with_select_related(self):
+ item1 = Item.objects.create(name="first", value=47)
+ item2 = Item.objects.create(name="second", value=42)
+ simple = SimpleItem.objects.create(name="simple", value="23")
+ related = ItemAndSimpleItem.objects.create(item=item1, simple=simple)
+
+ obj = ItemAndSimpleItem.objects.defer('item').select_related('simple').get()
+ self.assertEqual(obj.item, item1)
+ self.assertEqual(obj.item_id, item1.id)
+
+ obj.item = item2
+ obj.save()
+
+ obj = ItemAndSimpleItem.objects.defer('item').select_related('simple').get()
+ self.assertEqual(obj.item, item2)
+ self.assertEqual(obj.item_id, item2.id)
+
def test_deferred_class_factory(self):
from django.db.models.query_utils import deferred_class_factory
new_class = deferred_class_factory(Item,
View
2  tests/regressiontests/select_related_regress/tests.py
@@ -133,7 +133,7 @@ def test_regression_12851(self):
self.assertEqual(troy.state.name, 'Western Australia')
# Also works if you use only, rather than defer
- troy = SpecialClient.objects.select_related('state').only('name').get(name='Troy Buswell')
+ troy = SpecialClient.objects.select_related('state').only('name', 'state').get(name='Troy Buswell')
self.assertEqual(troy.name, 'Troy Buswell')
self.assertEqual(troy.value, 42)
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