Ensure sequences are reset correctly in the presence of swapped models.

django/db/backends/__init__.py

@@ -319,6 +319,7 @@ class BaseDatabaseWrapper(object):
     def make_debug_cursor(self, cursor):
         return util.CursorDebugWrapper(cursor, self)
 
+
 class BaseDatabaseFeatures(object):
     allows_group_by_pk = False
     # True if django.db.backend.utils.typecast_timestamp is used on values
@@ -776,7 +777,7 @@ class BaseDatabaseOperations(object):
         The `style` argument is a Style object as returned by either
         color_style() or no_style() in django.core.management.color.
         """
-        return [] # No sequence reset required by default.
+        return []  # No sequence reset required by default.
 
     def start_transaction_sql(self):
         """
@@ -915,6 +916,7 @@ class BaseDatabaseOperations(object):
         conn = ' %s ' % connector
         return conn.join(sub_expressions)
 
+
 class BaseDatabaseIntrospection(object):
     """
     This class encapsulates all backend-specific introspection utilities
@@ -1010,12 +1012,14 @@ class BaseDatabaseIntrospection(object):
             for model in models.get_models(app):
                 if not model._meta.managed:
                     continue
+                if model._meta.swapped:
+                    continue
                 if not router.allow_syncdb(self.connection.alias, model):
                     continue
                 for f in model._meta.local_fields:
                     if isinstance(f, models.AutoField):
                         sequence_list.append({'table': model._meta.db_table, 'column': f.column})
-                        break # Only one AutoField is allowed per model, so don't bother continuing.
+                        break  # Only one AutoField is allowed per model, so don't bother continuing.
 
                 for f in model._meta.local_many_to_many:
                     # If this is an m2m using an intermediate table,
@@ -1052,6 +1056,7 @@ class BaseDatabaseIntrospection(object):
         """
         raise NotImplementedError
 
+
 class BaseDatabaseClient(object):
     """
     This class encapsulates all backend-specific methods for opening a
@@ -1068,6 +1073,7 @@ class BaseDatabaseClient(object):
     def runshell(self):
         raise NotImplementedError()
 
+
 class BaseDatabaseValidation(object):
     """
     This class encapsualtes all backend-specific model validation.

tests/modeltests/proxy_models/tests.py

@@ -1,4 +1,5 @@
 from __future__ import absolute_import, unicode_literals
+import copy
 
 from django.conf import settings
 from django.contrib.contenttypes.models import ContentType
@@ -6,6 +7,7 @@ from django.core import management
 from django.core.exceptions import FieldError
 from django.db import models, DEFAULT_DB_ALIAS
 from django.db.models import signals
+from django.db.models.loading import cache
 from django.test import TestCase
 
 
@@ -147,6 +149,12 @@ class ProxyModelTests(TestCase):
 
     def test_swappable(self):
         try:
+            # This test adds dummy applications to the app cache. These
+            # need to be removed in order to prevent bad interactions
+            # with the flush operation in other tests.
+            old_app_models = copy.deepcopy(cache.app_models)
+            old_app_store = copy.deepcopy(cache.app_store)
+
             settings.TEST_SWAPPABLE_MODEL = 'proxy_models.AlternateModel'
 
             class SwappableModel(models.Model):
@@ -165,6 +173,8 @@ class ProxyModelTests(TestCase):
                         proxy = True
         finally:
             del settings.TEST_SWAPPABLE_MODEL
+            cache.app_models = old_app_models
+            cache.app_store = old_app_store
 
     def test_myperson_manager(self):
         Person.objects.create(name="fred")