Added a db_constraint option to ForeignKeys.
This controls whether or not a database level cosntraint is created. This is useful in a few specialized circumstances, but in general should not be used!
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@ -77,7 +77,7 @@ class BaseDatabaseCreation(object):
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tablespace, inline=True)
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if tablespace_sql:
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field_output.append(tablespace_sql)
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if f.rel:
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if f.rel and f.db_constraint:
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ref_output, pending = self.sql_for_inline_foreign_key_references(
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model, f, known_models, style)
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if pending:
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@ -981,9 +981,10 @@ class ForeignKey(RelatedField, Field):
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}
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description = _("Foreign Key (type determined by related field)")
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def __init__(self, to, to_field=None, rel_class=ManyToOneRel, **kwargs):
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def __init__(self, to, to_field=None, rel_class=ManyToOneRel,
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db_constraint=True, **kwargs):
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try:
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to_name = to._meta.model_name
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to._meta.model_name
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except AttributeError: # to._meta doesn't exist, so it must be RECURSIVE_RELATIONSHIP_CONSTANT
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assert isinstance(to, six.string_types), "%s(%r) is invalid. First parameter to ForeignKey must be either a model, a model name, or the string %r" % (self.__class__.__name__, to, RECURSIVE_RELATIONSHIP_CONSTANT)
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else:
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@ -997,13 +998,14 @@ class ForeignKey(RelatedField, Field):
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if 'db_index' not in kwargs:
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kwargs['db_index'] = True
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self.db_constraint = db_constraint
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kwargs['rel'] = rel_class(to, to_field,
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related_name=kwargs.pop('related_name', None),
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limit_choices_to=kwargs.pop('limit_choices_to', None),
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parent_link=kwargs.pop('parent_link', False),
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on_delete=kwargs.pop('on_delete', CASCADE),
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)
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Field.__init__(self, **kwargs)
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super(ForeignKey, self).__init__(**kwargs)
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def get_path_info(self):
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"""
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@ -1051,6 +1051,19 @@ define the details of how the relation works.
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The field on the related object that the relation is to. By default, Django
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uses the primary key of the related object.
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.. attribute:: ForeignKey.db_constraint
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Controls whether or not a constraint should be created in the database for
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this foreign key. The default is ``True``, and that's almost certainly what
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you want; setting this to ``False`` can be very bad for data integrity.
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That said, here are some scenarios where you might want to do this:
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* You have legacy data that is not valid.
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* You're sharding your database.
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If you use this, accessing a related object that doesn't exist will raise
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its ``DoesNotExist`` exception.
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.. attribute:: ForeignKey.on_delete
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When an object referenced by a :class:`ForeignKey` is deleted, Django by
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@ -85,6 +85,9 @@ Minor features
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:class:`~django.http.HttpResponsePermanentRedirect` now provide an ``url``
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attribute (equivalent to the URL the response will redirect to).
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* Added the :attr:`django.db.models.ForeignKey.db_constraint`
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option.
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Backwards incompatible changes in 1.6
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=====================================
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@ -86,3 +86,16 @@ class Item(models.Model):
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def __str__(self):
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return self.name
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@python_2_unicode_compatible
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class Object(models.Model):
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pass
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@python_2_unicode_compatible
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class ObjectReference(models.Model):
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obj = models.ForeignKey(Object, db_constraint=False)
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def __str__(self):
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return str(self.obj_id)
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@ -7,13 +7,12 @@ import threading
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from django.conf import settings
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from django.core.management.color import no_style
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from django.core.exceptions import ImproperlyConfigured
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from django.db import (backend, connection, connections, DEFAULT_DB_ALIAS,
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IntegrityError, transaction)
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from django.db.backends.signals import connection_created
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from django.db.backends.postgresql_psycopg2 import version as pg_version
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from django.db.models import fields, Sum, Avg, Variance, StdDev
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from django.db.utils import ConnectionHandler, DatabaseError, load_backend
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from django.db.models import Sum, Avg, Variance, StdDev
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from django.db.utils import ConnectionHandler, DatabaseError
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from django.test import (TestCase, skipUnlessDBFeature, skipIfDBFeature,
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TransactionTestCase)
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from django.test.utils import override_settings, str_prefix
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@ -724,3 +723,22 @@ class MySQLPKZeroTests(TestCase):
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def test_zero_as_autoval(self):
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with self.assertRaises(ValueError):
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models.Square.objects.create(id=0, root=0, square=1)
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class DBConstraintTestCase(TransactionTestCase):
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def test_can_reference_existant(self):
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obj = models.Object.objects.create()
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ref = models.ObjectReference.objects.create(obj=obj)
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self.assertEqual(ref.obj, obj)
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ref = models.ObjectReference.objects.get(obj=obj)
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self.assertEqual(ref.obj, obj)
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def test_can_reference_non_existant(self):
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self.assertFalse(models.Object.objects.filter(id=12345).exists())
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ref = models.ObjectReference.objects.create(obj_id=12345)
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ref_new = models.ObjectReference.objects.get(obj_id=12345)
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self.assertEqual(ref, ref_new)
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with self.assertRaises(models.Object.DoesNotExist):
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ref.obj
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