Ticket #17653: ticket_17653.diff

django/db/backends/__init__.py

@@ -640 +640 @@
         """
         return 'DEFAULT'
 
+    def validate_autopk_value(self, value):
+        """
+        Certain backends have limitations for what values can be used as
+        autofield values. This method will return True if the value is usable,
+        else False.
+        """
+        return True
+
     def process_clob(self, value):
         """
         Returns the value of a CLOB column, for backends that return a locator

django/db/backends/mysql/base.py

@@ -226 +226 @@
         # 2**64 - 1, as recommended by the MySQL documentation
         return 18446744073709551615L
 
+    def validate_autopk_value(self, value):
+        if value == 0:
+            return False
+        return True
+
     def quote_name(self, name):
         if name.startswith("`") and name.endswith("`"):
             return name # Quoting once is enough.

django/db/models/fields/__init__.py

@@ -535 +535 @@
             return None
         return int(value)
 
+    def get_db_prep_save(self, value, connection):
+        prepared = self.get_prep_value(value)
+        if not connection.ops.validate_autopk_value(prepared):
+            raise ValueError('The database backend does not accept %s as a '
+                             'value for field %s' % (prepared, self.name))
+        return prepared
+
     def contribute_to_class(self, cls, name):
         assert not cls._meta.has_auto_field, \
                "A model can't have more than one AutoField."

tests/regressiontests/backends/tests.py

@@ -618 +618 @@
         self.assertRaisesRegexp(ImproperlyConfigured,
             "Try using django.db.backends.sqlite3 instead",
             load_backend, 'sqlite3')
+
+class MySQLAutoValueTests(TestCase):
+    """
+    Test a bug in MySQL where zero as a value to autofield gets ignored.
+
+    As this test is safe to run on other backends, no need to skip them.
+    """
+    def test_zero_as_autoval(self):
+        models.Square.objects.create(id=0, root=0, square=1)
+        models.Square.objects.all().delete()
+        s = models.Square(id=0, root=0, square=1)
+        models.Square.objects.bulk_create([s])
+        models.Square.objects.all().delete()
+        s = models.Square(id=0, root=0, square=1)
+        s.save()