Ticket #16708: cached_db_exists_check_cache_v2.diff

django/contrib/sessions/tests.py

@@ -12 +12 @@
 from django.contrib.sessions.backends.signed_cookies import SessionStore as CookieSession
 from django.contrib.sessions.models import Session
 from django.contrib.sessions.middleware import SessionMiddleware
+from django.core.cache import cache
 from django.core.exceptions import ImproperlyConfigured, SuspiciousOperation
 from django.http import HttpResponse
 from django.test import TestCase, RequestFactory
@@ -276 +277 @@
         self.assertEqual(self.session['y'], 2)
 
 
+class MockDatabaseStore(DatabaseSession):
+    db_exists_called = False
+    db_exists_call_count = 0
+
+    def exists(self, session_key):
+        self.db_exists_called = True
+        self.db_exists_call_count += 1
+        return super(MockDatabaseStore, self).exists(session_key)
+
+class MockCacheDBSession(CacheDBSession, MockDatabaseStore):
+    pass
+
 class CacheDBSessionTests(SessionTestsMixin, TestCase):
 
-    backend = CacheDBSession
+    backend = MockCacheDBSession
 
+    def test_exists_cached(self):
+        self.session['cat'] = "dog"
+        self.session.save()
+
+        self.assertTrue(self.session.exists(self.session.session_key))
+
+        self.assertTrue(self.session.db_exists_called)
+        self.assertEqual(self.session.db_exists_call_count, 1)
+
+    def test_exists_not_cached(self):
+        self.session['cat'] = "dog"
+        self.session.save()
+
+        cache.delete(self.session.session_key)
+
+        self.assertTrue(self.session.exists(self.session.session_key))
+
+        self.assertTrue(self.session.db_exists_called)
+        self.assertEqual(self.session.db_exists_call_count, 2)
+
 # Don't need DB flushing for these tests, so can use unittest.TestCase as base class
 class FileSessionTests(SessionTestsMixin, unittest.TestCase):
 

django/contrib/sessions/backends/cached_db.py

@@ -22 +22 @@
         return data
 
     def exists(self, session_key):
+        if cache.get(session_key) is not None:
+            return True
         return super(SessionStore, self).exists(session_key)
 
     def save(self, must_create=False):