Use a simplier serializer and do the course counts as a single aggregate query

lms/djangoapps/api_manager/users/serializers.py

@@ -42,6 +42,15 @@ class UserSerializer(DynamicFieldsModelSerializer):
         fields = ("id", "email", "username", "first_name", "last_name", "created", "is_active", "organizations", "avatar_url", "city", "title", "country", "full_name")
         read_only_fields = ("id", "email", "username")
 
+class SimpleUserSerializer(DynamicFieldsModelSerializer):
+    created = serializers.DateTimeField(source='date_joined', required=False)
+
+    class Meta:
+        """ Serializer/field specification """
+        model = APIUser
+        fields = ("id", "email", "username", "first_name", "last_name", "created", "is_active")
+        read_only_fields = ("id", "email", "username")
+
 class UserCountByCitySerializer(serializers.Serializer):
     """ Serializer for user count by city """
     city = serializers.CharField(source='profile__city')

lms/djangoapps/organizations/tests.py

@@ -62,6 +62,14 @@ class OrganizationsApiTests(ModuleStoreTestCase):
         profile.city = 'Boston'
         profile.save()
 
+        self.test_user2 = User.objects.create(
+            email=str(uuid.uuid4()),
+            username=str(uuid.uuid4())
+        )
+        profile2 = UserProfile(user=self.test_user2)
+        profile2.city = 'NYC'
+        profile2.save()
+
         self.course = CourseFactory.create()
         self.second_course = CourseFactory.create(
             number="899"
@@ -322,6 +330,7 @@ class OrganizationsApiTests(ModuleStoreTestCase):
 
     def test_organizations_users_get_with_course_count(self):
         CourseEnrollmentFactory.create(user=self.test_user, course_id=self.course.id)
+        CourseEnrollmentFactory.create(user=self.test_user2, course_id=self.course.id)
         CourseEnrollmentFactory.create(user=self.test_user, course_id=self.second_course.id)
 
         data = {
@@ -338,10 +347,16 @@ class OrganizationsApiTests(ModuleStoreTestCase):
         data = {"id": self.test_user.id}
         response = self.do_post(users_uri, data)
         self.assertEqual(response.status_code, 201)
+
+        data = {"id": self.test_user2.id}
+        response = self.do_post(users_uri, data)
+        self.assertEqual(response.status_code, 201)
         response = self.do_get('{}{}'.format(users_uri, '?include_course_counts=True'))
         self.assertEqual(response.status_code, 200)
         self.assertEqual(response.data[0]['id'], self.test_user.id)
         self.assertEqual(response.data[0]['course_count'], 2)
+        self.assertEqual(response.data[1]['id'], self.test_user2.id)
+        self.assertEqual(response.data[1]['course_count'], 1)
 
     def test_organizations_users_get_with_grades(self):
         # Create 4 users

lms/djangoapps/organizations/views.py

@@ -12,7 +12,7 @@ from rest_framework.response import Response
 
 from api_manager.courseware_access import get_course_key, get_aggregate_exclusion_user_ids
 from organizations.models import Organization
-from api_manager.users.serializers import UserSerializer
+from api_manager.users.serializers import UserSerializer, SimpleUserSerializer
 from api_manager.groups.serializers import GroupSerializer
 from api_manager.utils import str2bool
 from gradebook.models import StudentGradebook
@@ -92,19 +92,28 @@ class OrganizationsViewSet(viewsets.ModelViewSet):
                 course_key = get_course_key(course_id)
 
             users = User.objects.filter(organizations=pk)
+
             if course_key:
                 users = users.filter(courseenrollment__course_id__exact=course_key,
                                      courseenrollment__is_active=True)
             if str2bool(include_grades):
                 users = users.select_related('studentgradebook')
+
+            if str2bool(include_course_counts):
+                enrollments = CourseEnrollment.objects.filter(user__in=users).values('user').order_by().annotate(total=Count('user'))
+                enrollments_by_user = {}
+                for enrollment in enrollments:
+                    enrollments_by_user[enrollment['user']] = enrollment['total']
+
             response_data = []
             if users:
                 for user in users:
-                    serializer = UserSerializer(user)
+                    serializer = SimpleUserSerializer(user)
                     user_data = serializer.data
+
                     if str2bool(include_course_counts):
-                        enrollments = CourseEnrollment.enrollments_for_user(user).count()
-                        user_data['course_count'] = enrollments
+                        user_data['course_count'] = enrollments_by_user.get(user.id, 0)
+
                     if str2bool(include_grades) and course_key:
                         user_grades = {'grade': 0, 'proforma_grade': 0}
                         gradebook = user.studentgradebook_set.filter(course_id=course_key)
@@ -114,6 +123,7 @@ class OrganizationsViewSet(viewsets.ModelViewSet):
                             user_grades['complete_status'] = True if 0 < gradebook[0].proforma_grade <= \
                                 gradebook[0].grade + grade_complete_match_range else False
                         user_data.update(user_grades)
+
                     response_data.append(user_data)
             return Response(response_data, status=status.HTTP_200_OK)
         else: