Improved performance of program API endpoint (#324)

ECOM-5559

course_discovery/apps/api/v1/tests/test_views/test_programs.py

@@ -2,7 +2,7 @@ import ddt
 from django.core.urlresolvers import reverse
 from rest_framework.test import APITestCase, APIRequestFactory
 
-from course_discovery.apps.api.serializers import ProgramSerializer
+from course_discovery.apps.api.serializers import ProgramSerializer, MinimalProgramSerializer
 from course_discovery.apps.core.tests.factories import USER_PASSWORD, UserFactory
 from course_discovery.apps.course_metadata.choices import ProgramStatus
 from course_discovery.apps.course_metadata.models import Program
@@ -40,15 +40,17 @@ class ProgramViewSetTests(APITestCase):
     def test_retrieve(self):
         """ Verify the endpoint returns the details for a single program. """
         program = ProgramFactory()
+        with self.assertNumQueries(15):
             self.assert_retrieve_success(program)
 
     def test_retrieve_without_course_runs(self):
         """ Verify the endpoint returns data for a program even if the program's courses have no course runs. """
         course = CourseFactory()
         program = ProgramFactory(courses=[course])
+        with self.assertNumQueries(15):
             self.assert_retrieve_success(program)
 
-    def assert_list_results(self, url, expected):
+    def assert_list_results(self, url, expected, expected_query_count):
         """
         Asserts the results serialized/returned at the URL matches those that are expected.
         Args:
@@ -62,27 +64,29 @@ class ProgramViewSetTests(APITestCase):
         Returns:
             None
         """
+        with self.assertNumQueries(expected_query_count):
             response = self.client.get(url)
+
         self.assertEqual(
             response.data['results'],
-            ProgramSerializer(expected, many=True, context={'request': self.request}).data
+            MinimalProgramSerializer(expected, many=True, context={'request': self.request}).data
         )
 
     def test_list(self):
         """ Verify the endpoint returns a list of all programs. """
         expected = ProgramFactory.create_batch(3)
         expected.reverse()
-        self.assert_list_results(self.list_path, expected)
+        self.assert_list_results(self.list_path, expected, 7)
 
     def test_filter_by_type(self):
         """ Verify that the endpoint filters programs to those of a given type. """
         program_type_name = 'foo'
         program = ProgramFactory(type__name=program_type_name)
         url = self.list_path + '?type=' + program_type_name
-        self.assert_list_results(url, [program])
+        self.assert_list_results(url, [program], 7)
 
         url = self.list_path + '?type=bar'
-        self.assert_list_results(url, [])
+        self.assert_list_results(url, [], 4)
 
     def test_filter_by_uuids(self):
         """ Verify that the endpoint filters programs to those matching the provided UUIDs. """
@@ -94,14 +98,14 @@ class ProgramViewSetTests(APITestCase):
         # Create a third program, which should be filtered out.
         ProgramFactory()
 
-        self.assert_list_results(url, expected)
+        self.assert_list_results(url, expected, 7)
 
     @ddt.data(
-        (ProgramStatus.Unpublished, False),
-        (ProgramStatus.Active, True),
+        (ProgramStatus.Unpublished, False, 4),
+        (ProgramStatus.Active, True, 7),
     )
     @ddt.unpack
-    def test_filter_by_marketable(self, status, is_marketable):
+    def test_filter_by_marketable(self, status, is_marketable, expected_query_count):
         """ Verify the endpoint filters programs to those that are marketable. """
         url = self.list_path + '?marketable=1'
         ProgramFactory(marketing_slug='')
@@ -110,4 +114,4 @@ class ProgramViewSetTests(APITestCase):
 
         expected = programs if is_marketable else []
         self.assertEqual(list(Program.objects.marketable()), expected)
-        self.assert_list_results(url, expected)
+        self.assert_list_results(url, expected, expected_query_count)

course_discovery/apps/api/v1/views.py

@@ -395,7 +395,6 @@ class ProgramViewSet(viewsets.ReadOnlyModelViewSet):
     lookup_value_regex = '[0-9a-f-]+'
     queryset = prefetch_related_objects_for_programs(Program.objects.all())
     permission_classes = (IsAuthenticated,)
-    serializer_class = serializers.ProgramSerializer
     filter_backends = (DjangoFilterBackend,)
     filter_class = filters.ProgramFilter
 
@@ -404,6 +403,12 @@ class ProgramViewSet(viewsets.ReadOnlyModelViewSet):
         context['published_course_runs_only'] = int(self.request.GET.get('published_course_runs_only', 0))
         return context
 
+    def get_serializer_class(self):
+        if self.action == 'list':
+            return serializers.MinimalProgramSerializer
+
+        return serializers.ProgramSerializer
+
     def list(self, request, *args, **kwargs):
         """ List all programs.
         ---