Fixed #20429 -- Added QuerySet.update_or_create

Thanks tunixman for the suggestion and Loic Bistuer for the review.

AUTHORS

@@ -530,6 +530,7 @@ answer newbie questions, and generally made Django that much better:
     Leo Shklovskii
     jason.sidabras@gmail.com
     Mikołaj Siedlarek <mikolaj.siedlarek@gmail.com>
+    Karol Sikora <elektrrrus@gmail.com>
     Brenton Simpson <http://theillustratedlife.com>
     Jozko Skrablin <jozko.skrablin@gmail.com>
     Ben Slavin <benjamin.slavin@gmail.com>

django/db/models/manager.py

@@ -154,6 +154,9 @@ class Manager(six.with_metaclass(RenameManagerMethods)):
     def get_or_create(self, **kwargs):
         return self.get_queryset().get_or_create(**kwargs)
 
+    def update_or_create(self, **kwargs):
+        return self.get_queryset().update_or_create(**kwargs)
+
     def create(self, **kwargs):
         return self.get_queryset().create(**kwargs)
 

django/db/models/query.py

@@ -364,37 +364,84 @@ class QuerySet(object):
 
         return objs
 
-    def get_or_create(self, **kwargs):
+    def get_or_create(self, defaults=None, **kwargs):
         """
         Looks up an object with the given kwargs, creating one if necessary.
         Returns a tuple of (object, created), where created is a boolean
         specifying whether an object was created.
         """
-        defaults = kwargs.pop('defaults', {})
-        lookup = kwargs.copy()
-        for f in self.model._meta.fields:
-            if f.attname in lookup:
-                lookup[f.name] = lookup.pop(f.attname)
+        lookup, params, _ = self._extract_model_params(defaults, **kwargs)
         try:
             self._for_write = True
             return self.get(**lookup), False
         except self.model.DoesNotExist:
+            return self._create_object_from_params(lookup, params)
+
+    def update_or_create(self, defaults=None, **kwargs):
+        """
+        Looks up an object with the given kwargs, updating one with defaults
+        if it exists, otherwise creates a new one.
+        Returns a tuple (object, created), where created is a boolean
+        specifying whether an object was created.
+        """
+        lookup, params, filtered_defaults = self._extract_model_params(defaults, **kwargs)
+        try:
+            self._for_write = True
+            obj = self.get(**lookup)
+        except self.model.DoesNotExist:
+            obj, created = self._create_object_from_params(lookup, params)
+            if created:
+                return obj, created
+        for k, v in six.iteritems(filtered_defaults):
+            setattr(obj, k, v)
+        try:
+            sid = transaction.savepoint(using=self.db)
+            obj.save(update_fields=filtered_defaults.keys(), using=self.db)
+            transaction.savepoint_commit(sid, using=self.db)
+            return obj, False
+        except DatabaseError:
+            transaction.savepoint_rollback(sid, using=self.db)
+            six.reraise(sys.exc_info())
+
+    def _create_object_from_params(self, lookup, params):
+        """
+        Tries to create an object using passed params.
+        Used by get_or_create and update_or_create
+        """
+        try:
+            obj = self.model(**params)
+            sid = transaction.savepoint(using=self.db)
+            obj.save(force_insert=True, using=self.db)
+            transaction.savepoint_commit(sid, using=self.db)
+            return obj, True
+        except DatabaseError:
+            transaction.savepoint_rollback(sid, using=self.db)
+            exc_info = sys.exc_info()
             try:
-                params = dict((k, v) for k, v in kwargs.items() if LOOKUP_SEP not in k)
-                params.update(defaults)
-                obj = self.model(**params)
-                sid = transaction.savepoint(using=self.db)
-                obj.save(force_insert=True, using=self.db)
-                transaction.savepoint_commit(sid, using=self.db)
-                return obj, True
-            except DatabaseError:
-                transaction.savepoint_rollback(sid, using=self.db)
-                exc_info = sys.exc_info()
-                try:
-                    return self.get(**lookup), False
-                except self.model.DoesNotExist:
-                    # Re-raise the DatabaseError with its original traceback.
-                    six.reraise(*exc_info)
+                return self.get(**lookup), False
+            except self.model.DoesNotExist:
+                # Re-raise the DatabaseError with its original traceback.
+                six.reraise(*exc_info)
+
+    def _extract_model_params(self, defaults, **kwargs):
+        """
+        Prepares `lookup` (kwargs that are valid model attributes), `params`
+        (for creating a model instance) and `filtered_defaults` (defaults
+        that are valid model attributes) based on given kwargs; for use by
+        get_or_create and update_or_create.
+        """
+        defaults = defaults or {}
+        filtered_defaults = {}
+        lookup = kwargs.copy()
+        for f in self.model._meta.fields:
+            # Filter out fields that don't belongs to the model.
+            if f.attname in lookup:
+                lookup[f.name] = lookup.pop(f.attname)
+            if f.attname in defaults:
+                filtered_defaults[f.name] = defaults.pop(f.attname)
+        params = dict((k, v) for k, v in kwargs.items() if LOOKUP_SEP not in k)
+        params.update(filtered_defaults)
+        return lookup, params, filtered_defaults
 
     def _earliest_or_latest(self, field_name=None, direction="-"):
         """

docs/ref/models/querysets.txt

@@ -1330,7 +1330,7 @@ prepared to handle the exception if you are using manual primary keys.
 get_or_create
 ~~~~~~~~~~~~~
 
-.. method:: get_or_create(**kwargs)
+.. method:: get_or_create(defaults=None, **kwargs)
 
 A convenience method for looking up an object with the given ``kwargs`` (may be
 empty if your model has defaults for all fields), creating one if necessary.
@@ -1366,7 +1366,6 @@ found, ``get_or_create()`` will instantiate and save a new object, returning a
 tuple of the new object and ``True``. The new object will be created roughly
 according to this algorithm::
 
-    defaults = kwargs.pop('defaults', {})
     params = dict([(k, v) for k, v in kwargs.items() if '__' not in k])
     params.update(defaults)
     obj = self.model(**params)
@@ -1447,6 +1446,49 @@ in the HTTP spec.
   chapter because it isn't related to that book, but it can't create it either
   because ``title`` field should be unique.
 
+update_or_create
+~~~~~~~~~~~~~~~~
+
+.. method:: update_or_create(defaults=None, **kwargs)
+
+.. versionadded:: 1.7
+
+A convenience method for updating an object with the given ``kwargs``, creating
+a new one if necessary. The ``defaults`` is a dictionary of (field, value)
+pairs used to update the object.
+
+Returns a tuple of ``(object, created)``, where ``object`` is the created or
+updated object and ``created`` is a boolean specifying whether a new object was
+created.
+
+The ``update_or_create`` method tries to fetch an object from database based on
+the given ``kwargs``. If a match is found, it updates the fields passed in the
+``defaults`` dictionary.
+
+This is meant as a shortcut to boilerplatish code. For example::
+
+    try:
+        obj = Person.objects.get(first_name='John', last_name='Lennon')
+        for key, value in updated_values.iteritems():
+            setattr(obj, key, value)
+        obj.save()
+    except Person.DoesNotExist:
+        updated_values.update({'first_name': 'John', 'last_name': 'Lennon'})
+        obj = Person(**updated_values)
+        obj.save()
+
+This pattern gets quite unwieldy as the number of fields in a model goes up.
+The above example can be rewritten using ``update_or_create()`` like so::
+
+    obj, created = Person.objects.update_or_create(
+        first_name='John', last_name='Lennon', defaults=updated_values)
+
+For detailed description how names passed in ``kwargs`` are resolved see
+:meth:`get_or_create`.
+
+As described above in :meth:`get_or_create`, this method is prone to a
+race-condition which can result in multiple rows being inserted simultaneously
+if uniqueness is not enforced at the database level.
 
 bulk_create
 ~~~~~~~~~~~

docs/releases/1.7.txt

@@ -41,6 +41,9 @@ Minor features
 * The ``enter`` argument was added to the
   :data:`~django.test.signals.setting_changed` signal.
 
+* The :meth:`QuerySet.update_or_create()
+  <django.db.models.query.QuerySet.update_or_create>` method was added.
+
 Backwards incompatible changes in 1.7
 =====================================
 

tests/get_or_create/tests.py

@@ -131,3 +131,68 @@ class GetOrCreateThroughManyToMany(TestCase):
         Tag.objects.create(text='foo')
         a_thing = Thing.objects.create(name='a')
         self.assertRaises(IntegrityError, a_thing.tags.get_or_create, text='foo')
+
+
+class UpdateOrCreateTests(TestCase):
+
+    def test_update(self):
+        Person.objects.create(
+            first_name='John', last_name='Lennon', birthday=date(1940, 10, 9)
+        )
+        p, created = Person.objects.update_or_create(
+            first_name='John', last_name='Lennon', defaults={
+                'birthday': date(1940, 10, 10)
+            }
+        )
+        self.assertFalse(created)
+        self.assertEqual(p.first_name, 'John')
+        self.assertEqual(p.last_name, 'Lennon')
+        self.assertEqual(p.birthday, date(1940, 10, 10))
+
+    def test_create(self):
+        p, created = Person.objects.update_or_create(
+            first_name='John', last_name='Lennon', defaults={
+                'birthday': date(1940, 10, 10)
+            }
+        )
+        self.assertTrue(created)
+        self.assertEqual(p.first_name, 'John')
+        self.assertEqual(p.last_name, 'Lennon')
+        self.assertEqual(p.birthday, date(1940, 10, 10))
+
+    def test_create_twice(self):
+        params = {
+            'first_name': 'John',
+            'last_name': 'Lennon',
+            'birthday': date(1940, 10, 10),
+        }
+        Person.objects.update_or_create(**params)
+        # If we execute the exact same statement, it won't create a Person.
+        p, created = Person.objects.update_or_create(**params)
+        self.assertFalse(created)
+
+    def test_integrity(self):
+        # If you don't specify a value or default value for all required
+        # fields, you will get an error.
+        self.assertRaises(IntegrityError,
+            Person.objects.update_or_create, first_name="Tom", last_name="Smith")
+
+    def test_mananual_primary_key_test(self):
+        # If you specify an existing primary key, but different other fields,
+        # then you will get an error and data will not be updated.
+        ManualPrimaryKeyTest.objects.create(id=1, data="Original")
+        self.assertRaises(IntegrityError,
+            ManualPrimaryKeyTest.objects.update_or_create, id=1, data="Different"
+        )
+        self.assertEqual(ManualPrimaryKeyTest.objects.get(id=1).data, "Original")
+
+    def test_error_contains_full_traceback(self):
+        # update_or_create should raise IntegrityErrors with the full traceback.
+        # This is tested by checking that a known method call is in the traceback.
+        # We cannot use assertRaises/assertRaises here because we need to inspect
+        # the actual traceback. Refs #16340.
+        try:
+            ManualPrimaryKeyTest.objects.update_or_create(id=1, data="Different")
+        except IntegrityError as e:
+            formatted_traceback = traceback.format_exc()
+            self.assertIn('obj.save', formatted_traceback)