Fixed model.__eq__ and __hash__ for no pk value cases

The __eq__ method now considers two instances without primary key value
equal only when they have same id(). The __hash__ method raises
TypeError for no primary key case.

Fixed #18864, fixed #18250

Thanks to Tim Graham for docs review.
This commit is contained in:
Anssi Kääriäinen 2013-08-14 11:05:01 +03:00
parent 768bbf3efe
commit 6af05e7a0f
5 changed files with 53 additions and 4 deletions

View File

@ -459,14 +459,21 @@ class Model(six.with_metaclass(ModelBase)):
return '%s object' % self.__class__.__name__
def __eq__(self, other):
return (isinstance(other, Model) and
self._meta.concrete_model == other._meta.concrete_model and
self._get_pk_val() == other._get_pk_val())
if not isinstance(other, Model):
return False
if self._meta.concrete_model != other._meta.concrete_model:
return False
my_pk = self._get_pk_val()
if my_pk is None:
return self is other
return my_pk == other._get_pk_val()
def __ne__(self, other):
return not self.__eq__(other)
def __hash__(self):
if self._get_pk_val() is None:
raise TypeError("Model instances without primary key value are unhashable")
return hash(self._get_pk_val())
def __reduce__(self):

View File

@ -631,7 +631,11 @@ class BaseModelFormSet(BaseFormSet):
seen_data = set()
for form in valid_forms:
# get data for each field of each of unique_check
row_data = tuple([form.cleaned_data[field] for field in unique_check if field in form.cleaned_data])
row_data = (form.cleaned_data[field]
for field in unique_check if field in form.cleaned_data)
# Reduce Model instances to their primary key values
row_data = tuple(d._get_pk_val() if hasattr(d, '_get_pk_val') else d
for d in row_data)
if row_data and not None in row_data:
# if we've already seen it then we have a uniqueness failure
if row_data in seen_data:

View File

@ -521,6 +521,25 @@ For example::
In previous versions only instances of the exact same class and same
primary key value were considered equal.
``__hash__``
------------
.. method:: Model.__hash__()
The ``__hash__`` method is based on the instance's primary key value. It
is effectively hash(obj.pk). If the instance doesn't have a primary key
value then a ``TypeError`` will be raised (otherwise the ``__hash__``
method would return different values before and after the instance is
saved, but changing the ``__hash__`` value of an instance `is forbidden
in Python`_).
.. versionchanged:: 1.7
In previous versions instance's without primary key value were
hashable.
.. _is forbidden in Python: http://docs.python.org/reference/datamodel.html#object.__hash__
``get_absolute_url``
--------------------

View File

@ -199,6 +199,14 @@ Miscellaneous
equal when primary keys match. Previously only instances of exact same
class were considered equal on primary key match.
* The :meth:`django.db.models.Model.__eq__` method has changed such that
two ``Model`` instances without primary key values won't be considered
equal (unless they are the same instance).
* The :meth:`django.db.models.Model.__hash__` will now raise ``TypeError``
when called on an instance without a primary key value. This is done to
avoid mutable ``__hash__`` values in containers.
Features deprecated in 1.7
==========================

View File

@ -708,9 +708,20 @@ class ModelTest(TestCase):
SelfRef.objects.get(selfref=sr)
def test_eq(self):
self.assertEqual(Article(id=1), Article(id=1))
self.assertNotEqual(Article(id=1), object())
self.assertNotEqual(object(), Article(id=1))
a = Article()
self.assertEqual(a, a)
self.assertNotEqual(Article(), a)
def test_hash(self):
# Value based on PK
self.assertEqual(hash(Article(id=1)), hash(1))
with self.assertRaises(TypeError):
# No PK value -> unhashable (because save() would then change
# hash)
hash(Article())
class ConcurrentSaveTests(TransactionTestCase):