Added stores_state attribute for xmoduledescriptors as a way to declare if the module stores state in the database.

common/lib/xmodule/xmodule/capa_module.py

@@ -562,6 +562,8 @@ class CapaDescriptor(RawDescriptor):
     """
 
     module_class = CapaModule
+    
+    stores_state = True
 
     # VS[compat]
     # TODO (cpennington): Delete this method once all fall 2012 course are being

common/lib/xmodule/xmodule/seq_module.py

@@ -107,6 +107,8 @@ class SequenceModule(XModule):
 class SequenceDescriptor(MakoModuleDescriptor, XmlDescriptor):
     mako_template = 'widgets/sequence-edit.html'
     module_class = SequenceModule
+    
+    stores_state = True # For remembering where in the sequence the student is
 
     @classmethod
     def definition_from_xml(cls, xml_object, system):

common/lib/xmodule/xmodule/video_module.py

@@ -80,3 +80,5 @@ class VideoModule(XModule):
 
 class VideoDescriptor(RawDescriptor):
     module_class = VideoModule
+    
+    stores_state = True

common/lib/xmodule/xmodule/x_module.py

@@ -303,6 +303,10 @@ class XModuleDescriptor(Plugin, HTMLSnippet):
     """
     entry_point = "xmodule.v1"
     module_class = XModule
+    
+    # Attributes for inpsection of the descriptor
+    stores_state = False # Indicates wether the xmodule state should be 
+    # stored in a database (independent of shared state)
 
     # A list of metadata that this module can inherit from its parent module
     inheritable_metadata = (

lms/djangoapps/courseware/grades.py

@@ -183,6 +183,10 @@ def get_score(user, problem, student_module_cache):
     problem: an XModule
     cache: A StudentModuleCache
     """
+    if not problem.descriptor.stores_state:
+        # These are not problems, and do not store state
+        return (None, None)
+    
     correct = 0.0
 
     # If the ID is not in the cache, add the item

lms/djangoapps/courseware/models.py

@@ -69,10 +69,10 @@ class StudentModuleCache(object):
     """
     def __init__(self, user, descriptors):
         '''
-        Find any StudentModule objects that are needed by any child modules of the
-        supplied descriptor, or caches only the StudentModule objects specifically
-        for every descriptor in descriptors. Avoids making multiple queries to the 
-        database.
+        Find any StudentModule objects that are needed by any descriptor
+        in descriptors. Avoids making multiple queries to the database.
+        Note: Only modules that have store_state = True or have shared
+        state will have a StudentModule.
         
         Arguments
         user: The user for which to fetch maching StudentModules
@@ -134,7 +134,8 @@ class StudentModuleCache(object):
         '''
         keys = []
         for descriptor in descriptors:
-            keys.append(descriptor.location.url())
+            if descriptor.stores_state:
+                keys.append(descriptor.location.url())
             
             shared_state_key = getattr(descriptor, 'shared_state_key', None)
             if shared_state_key is not None:

lms/djangoapps/courseware/module_render.py

@@ -127,19 +127,18 @@ def get_module(user, request, location, student_module_cache, position=None):
     descriptor = modulestore().get_item(location)
     
     #TODO Only check the cache if this module can possibly have state
+    instance_module = None
+    shared_module = None
     if user.is_authenticated():
-        instance_module = student_module_cache.lookup(descriptor.category,
-                                              descriptor.location.url())
+        if descriptor.stores_state:
+            instance_module = student_module_cache.lookup(descriptor.category,
+                                                  descriptor.location.url())
         
         shared_state_key = getattr(descriptor, 'shared_state_key', None)
         if shared_state_key is not None:
             shared_module = student_module_cache.lookup(descriptor.category,
                                                         shared_state_key)
-        else:
-            shared_module = None
-    else:
-        instance_module = None
-        shared_module = None
+        
         
 
     instance_state = instance_module.state if instance_module is not None else None
@@ -206,6 +205,11 @@ def get_instance_module(user, module, student_module_cache):
         or None if this is an anonymous user
     """
     if user.is_authenticated():
+        if not module.descriptor.stores_state:
+            log.exception("Attempted to get the instance_module for a module " 
+                          + str(module.id) + " which does not store state.")
+            return None
+        
         instance_module = student_module_cache.lookup(module.category,
                                               module.location.url())