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b6c356b7bb
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.
186 lines
7.2 KiB
Python
186 lines
7.2 KiB
Python
from __future__ import absolute_import
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from django.db.models.query_utils import DeferredAttribute, InvalidQuery
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from django.test import TestCase
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from .models import Secondary, Primary, Child, BigChild, ChildProxy
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class DeferTests(TestCase):
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def assert_delayed(self, obj, num):
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count = 0
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for field in obj._meta.fields:
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if isinstance(obj.__class__.__dict__.get(field.attname),
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DeferredAttribute):
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count += 1
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self.assertEqual(count, num)
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def test_defer(self):
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# To all outward appearances, instances with deferred fields look the
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# same as normal instances when we examine attribute values. Therefore
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# we test for the number of deferred fields on returned instances (by
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# poking at the internals), as a way to observe what is going on.
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s1 = Secondary.objects.create(first="x1", second="y1")
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p1 = Primary.objects.create(name="p1", value="xx", related=s1)
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qs = Primary.objects.all()
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self.assert_delayed(qs.defer("name")[0], 1)
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self.assert_delayed(qs.only("name")[0], 2)
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self.assert_delayed(qs.defer("related__first")[0], 0)
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# Using 'pk' with only() should result in 3 deferred fields, namely all
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# of them except the model's primary key see #15494
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self.assert_delayed(qs.only("pk")[0], 3)
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obj = qs.select_related().only("related__first")[0]
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self.assert_delayed(obj, 2)
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self.assertEqual(obj.related_id, s1.pk)
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# You can use 'pk' with reverse foreign key lookups.
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self.assert_delayed(s1.primary_set.all().only('pk')[0], 3)
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self.assert_delayed(qs.defer("name").extra(select={"a": 1})[0], 1)
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self.assert_delayed(qs.extra(select={"a": 1}).defer("name")[0], 1)
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self.assert_delayed(qs.defer("name").defer("value")[0], 2)
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self.assert_delayed(qs.only("name").only("value")[0], 2)
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self.assert_delayed(qs.only("name").defer("value")[0], 2)
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self.assert_delayed(qs.only("name", "value").defer("value")[0], 2)
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self.assert_delayed(qs.defer("name").only("value")[0], 2)
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obj = qs.only()[0]
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self.assert_delayed(qs.defer(None)[0], 0)
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self.assert_delayed(qs.only("name").defer(None)[0], 0)
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# User values() won't defer anything (you get the full list of
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# dictionaries back), but it still works.
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self.assertEqual(qs.defer("name").values()[0], {
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"id": p1.id,
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"name": "p1",
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"value": "xx",
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"related_id": s1.id,
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})
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self.assertEqual(qs.only("name").values()[0], {
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"id": p1.id,
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"name": "p1",
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"value": "xx",
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"related_id": s1.id,
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})
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# Using defer() and only() with get() is also valid.
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self.assert_delayed(qs.defer("name").get(pk=p1.pk), 1)
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self.assert_delayed(qs.only("name").get(pk=p1.pk), 2)
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# When we defer a field and also select_related it, the query is
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# invalid and raises an exception.
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with self.assertRaises(InvalidQuery):
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qs.only("name").select_related("related")[0]
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with self.assertRaises(InvalidQuery):
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qs.defer("related").select_related("related")[0]
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# With a depth-based select_related, all deferred ForeignKeys are
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# deferred instead of traversed.
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with self.assertNumQueries(3):
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obj = qs.defer("related").select_related()[0]
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self.assert_delayed(obj, 1)
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self.assertEqual(obj.related.id, s1.pk)
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# Saving models with deferred fields is possible (but inefficient,
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# since every field has to be retrieved first).
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obj = Primary.objects.defer("value").get(name="p1")
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obj.name = "a new name"
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obj.save()
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self.assertQuerysetEqual(
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Primary.objects.all(), [
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"a new name",
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],
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lambda p: p.name
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)
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# Regression for #10572 - A subclass with no extra fields can defer
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# fields from the base class
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Child.objects.create(name="c1", value="foo", related=s1)
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# You can defer a field on a baseclass when the subclass has no fields
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obj = Child.objects.defer("value").get(name="c1")
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self.assert_delayed(obj, 1)
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self.assertEqual(obj.name, "c1")
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self.assertEqual(obj.value, "foo")
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obj.name = "c2"
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obj.save()
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# You can retrive a single column on a base class with no fields
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obj = Child.objects.only("name").get(name="c2")
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self.assert_delayed(obj, 3)
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self.assertEqual(obj.name, "c2")
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self.assertEqual(obj.value, "foo")
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obj.name = "cc"
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obj.save()
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BigChild.objects.create(name="b1", value="foo", related=s1, other="bar")
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# You can defer a field on a baseclass
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obj = BigChild.objects.defer("value").get(name="b1")
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self.assert_delayed(obj, 1)
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self.assertEqual(obj.name, "b1")
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self.assertEqual(obj.value, "foo")
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self.assertEqual(obj.other, "bar")
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obj.name = "b2"
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obj.save()
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# You can defer a field on a subclass
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obj = BigChild.objects.defer("other").get(name="b2")
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self.assert_delayed(obj, 1)
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self.assertEqual(obj.name, "b2")
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self.assertEqual(obj.value, "foo")
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self.assertEqual(obj.other, "bar")
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obj.name = "b3"
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obj.save()
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# You can retrieve a single field on a baseclass
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obj = BigChild.objects.only("name").get(name="b3")
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self.assert_delayed(obj, 4)
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self.assertEqual(obj.name, "b3")
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self.assertEqual(obj.value, "foo")
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self.assertEqual(obj.other, "bar")
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obj.name = "b4"
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obj.save()
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# You can retrieve a single field on a baseclass
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obj = BigChild.objects.only("other").get(name="b4")
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self.assert_delayed(obj, 4)
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self.assertEqual(obj.name, "b4")
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self.assertEqual(obj.value, "foo")
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self.assertEqual(obj.other, "bar")
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obj.name = "bb"
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obj.save()
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def test_defer_proxy(self):
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"""
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Ensure select_related together with only on a proxy model behaves
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as expected. See #17876.
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"""
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related = Secondary.objects.create(first='x1', second='x2')
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ChildProxy.objects.create(name='p1', value='xx', related=related)
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children = ChildProxy.objects.all().select_related().only('id', 'name')
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self.assertEqual(len(children), 1)
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child = children[0]
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self.assert_delayed(child, 2)
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self.assertEqual(child.name, 'p1')
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self.assertEqual(child.value, 'xx')
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def test_defer_inheritance_pk_chaining(self):
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"""
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When an inherited model is fetched from the DB, its PK is also fetched.
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When getting the PK of the parent model it is useful to use the already
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fetched parent model PK if it happens to be available. Tests that this
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is done.
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"""
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s1 = Secondary.objects.create(first="x1", second="y1")
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bc = BigChild.objects.create(name="b1", value="foo", related=s1,
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other="bar")
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bc_deferred = BigChild.objects.only('name').get(pk=bc.pk)
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with self.assertNumQueries(0):
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bc_deferred.id
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self.assertEqual(bc_deferred.pk, bc_deferred.id)
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