Revert "Improve the performance of access checking for a specific user in CourseViewList by prefetching data"

This reverts commit a2a340bcd0.

common/djangoapps/django_comment_common/models.py

@@ -121,14 +121,7 @@ class Role(models.Model):
         """
         Returns True if the user has one of the given roles for the given course
         """
-        if 'roles' in getattr(user, '_prefetched_objects_cache', {}):
-            # Don't blow up the prefetch cache
-            return any(
-                role.course_id == course_id and role.name in role_names
-                for role in user.roles.all()
-            )
-        else:
-            return user.roles.filter(course_id=course_id, name__in=role_names).exists()
+        return Role.objects.filter(course_id=course_id, name__in=role_names, users=user).exists()
 
 
 class Permission(models.Model):

common/djangoapps/student/models.py

@@ -1195,19 +1195,13 @@ class CourseEnrollment(models.Model):
         if user.is_anonymous:
             return None
         try:
-            if 'courseenrollment' in getattr(user, '_prefetched_objects_cache', {}):
-                for enrollment in user.courseenrollment_set.all():
-                    if enrollment.course_id == course_key:
-                        return enrollment
-                return None
-            else:
-                query = cls.objects
-                if select_related is not None:
-                    query = query.select_related(*select_related)
-                return query.get(
-                    user=user,
-                    course_id=course_key
-                )
+            query = cls.objects
+            if select_related is not None:
+                query = query.select_related(*select_related)
+            return query.get(
+                user=user,
+                course_id=course_key
+            )
         except cls.DoesNotExist:
             return None