148 lines
5.5 KiB
Python
148 lines
5.5 KiB
Python
from __future__ import absolute_import
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from django.db.models.query_utils import DeferredAttribute
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from django.test import TestCase
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from .models import Secondary, Primary, Child, BigChild
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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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# DOES THIS WORK?
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self.assert_delayed(qs.only("name").select_related("related")[0], 1)
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self.assert_delayed(qs.defer("related").select_related("related")[0], 0)
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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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