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Code Issues 32 Releases Wiki Activity

Fixed #17485 -- Made defer work with select_related

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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.
This commit is contained in:
Anssi Kääriäinen
2012-06-26 18:08:42 +03:00
parent 5318783027
commit b6c356b7bb
9 changed files with 81 additions and 21 deletions
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7
django/db/models/query.py
View File

@@ -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)

13
django/db/models/query_utils.py
View File

@@ -126,18 +126,19 @@ class DeferredAttribute(object):
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

7
django/db/models/sql/compiler.py
View File

@@ -596,6 +596,7 @@ class SQLCompiler(object):
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 @@ class SQLCompiler(object):
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 @@ class SQLCompiler(object):
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

12
django/db/models/sql/query.py
View File

@@ -1845,9 +1845,15 @@ class Query(object):
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):
"""

11
docs/ref/models/querysets.txt
View File

@@ -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
~~~~~

20
tests/modeltests/defer/tests.py
View File

@@ -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 @@ class DeferTests(TestCase):
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 @@ class DeferTests(TestCase):
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')

4
tests/regressiontests/defer_regress/models.py
View File

@@ -47,3 +47,7 @@ class SimpleItem(models.Model):
class Feature(models.Model):
item = models.ForeignKey(SimpleItem)
class ItemAndSimpleItem(models.Model):
item = models.ForeignKey(Item)
simple = models.ForeignKey(SimpleItem)

26
tests/regressiontests/defer_regress/tests.py
View File

@@ -9,7 +9,7 @@ from django.db.models.loading import cache
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 @@ class DeferRegressionTest(TestCase):
Child,
Feature,
Item,
ItemAndSimpleItem,
Leaf,
Proxy,
RelatedItem,
@@ -125,12 +126,16 @@ class DeferRegressionTest(TestCase):
),
)
)
# 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 @@ class DeferRegressionTest(TestCase):
"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 @@ class DeferRegressionTest(TestCase):
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,

2
tests/regressiontests/select_related_regress/tests.py
View File

@@ -133,7 +133,7 @@ class SelectRelatedRegressTests(TestCase):
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)