ug fixes to StudentModel caching. Added cache-update on db-update because we do POST/GET pairings for submitting answers and checking them.

--HG--
branch : dormsbee_performance

courseware/module_render.py

@@ -48,13 +48,13 @@ def make_track_function(request):
 def modx_dispatch(request, module=None, dispatch=None, id=None):
     ''' Generic view for extensions. '''
     # Grab the student information for the module from the database
-    s = StudentModule.objects.filter(student=request.user, 
-                                     module_id=id)
-    if len(s) == 0:
+    #s = StudentModule.objects.filter(student=request.user, 
+    #                                 module_id=id)
+    s = StudentModule.get_from_cache(request.user, id)
+    if s is None:
         log.debug("Couldnt find module for user and id " + str(module) + " " + str(request.user) + " "+ str(id))
         raise Http404
 
-    s=s[0]
     oldgrade = s.grade
     oldstate = s.state