Do not persist anonymous ids when exporting for all students of a course.

For large courses this causes export to take a long time and to time out.

LMS-2747

common/djangoapps/student/models.py

@@ -67,12 +67,15 @@ class AnonymousUserId(models.Model):
     unique_together = (user, course_id)
 
 
-def anonymous_id_for_user(user, course_id):
+def anonymous_id_for_user(user, course_id, save=True):
     """
     Return a unique id for a (user, course) pair, suitable for inserting
     into e.g. personalized survey links.
 
     If user is an `AnonymousUser`, returns `None`
+
+    Keyword arguments:
+    save -- Whether the id should be saved in an AnonymousUserId object.
     """
     # This part is for ability to get xblock instance in xblock_noauth handlers, where user is unauthenticated.
     if user.is_anonymous():
@@ -90,6 +93,14 @@ def anonymous_id_for_user(user, course_id):
         hasher.update(course_id.to_deprecated_string())
     digest = hasher.hexdigest()
 
+    if not hasattr(user, '_anonymous_id'):
+        user._anonymous_id = {}  # pylint: disable=protected-access
+
+    user._anonymous_id[course_id] = digest  # pylint: disable=protected-access
+
+    if save is False:
+        return digest
+
     try:
         anonymous_user_id, __ = AnonymousUserId.objects.get_or_create(
             defaults={'anonymous_user_id': digest},
@@ -111,11 +122,6 @@ def anonymous_id_for_user(user, course_id):
         # continue
         pass
 
-    if not hasattr(user, '_anonymous_id'):
-        user._anonymous_id = {}
-
-    user._anonymous_id[course_id] = digest
-
     return digest
 
 
@@ -263,14 +269,17 @@ class UserProfile(models.Model):
         self.save()
 
 
-def unique_id_for_user(user):
+def unique_id_for_user(user, save=True):
     """
     Return a unique id for a user, suitable for inserting into
     e.g. personalized survey links.
+
+    Keyword arguments:
+    save -- Whether the id should be saved in an AnonymousUserId object.
     """
     # Setting course_id to '' makes it not affect the generated hash,
     # and thus produce the old per-student anonymous id
-    return anonymous_id_for_user(user, None)
+    return anonymous_id_for_user(user, None, save=save)
 
 
 # TODO: Should be renamed to generic UserGroup, and possibly

common/djangoapps/student/tests/tests.py

@@ -491,3 +491,4 @@ class AnonymousLookupTable(TestCase):
         anonymous_id = anonymous_id_for_user(self.user, self.course.id)
         real_user = user_by_anonymous_id(anonymous_id)
         self.assertEqual(self.user, real_user)
+        self.assertEqual(anonymous_id, anonymous_id_for_user(self.user, self.course.id, save=False))

lms/djangoapps/instructor/tests/test_api.py

@@ -1334,7 +1334,7 @@ class TestInstructorAPILevelsDataDump(ModuleStoreTestCase, LoginEnrollmentTestCa
         self.assertEqual(response['Content-Type'], 'text/csv')
         body = response.content.replace('\r', '')
         self.assertTrue(body.startswith(
-            '"User ID","Anonymized user ID","Course Specific Anonymized user ID"'
+            '"User ID","Anonymized User ID","Course Specific Anonymized User ID"'
             '\n"2","41","42"\n'
         ))
         self.assertTrue(body.endswith('"7","41","42"\n'))

lms/djangoapps/instructor/tests/test_legacy_anon_csv.py

@@ -63,6 +63,6 @@ class TestInstructorDashboardAnonCSV(ModuleStoreTestCase, LoginEnrollmentTestCas
         body = response.content.replace('\r', '')
         self.assertEqual(
             body,
-            ('"User ID","Anonymized user ID","Course Specific Anonymized user ID"'
+            ('"User ID","Anonymized User ID","Course Specific Anonymized User ID"'
              '\n"2","41","42"\n')
         )

lms/djangoapps/instructor/views/api.py

@@ -630,8 +630,8 @@ def get_anon_ids(request, course_id):  # pylint: disable=W0613
     students = User.objects.filter(
         courseenrollment__course_id=course_id,
     ).order_by('id')
-    header = ['User ID', 'Anonymized user ID', 'Course Specific Anonymized user ID']
-    rows = [[s.id, unique_id_for_user(s), anonymous_id_for_user(s, course_id)] for s in students]
+    header = ['User ID', 'Anonymized User ID', 'Course Specific Anonymized User ID']
+    rows = [[s.id, unique_id_for_user(s, save=False), anonymous_id_for_user(s, course_id, save=False)] for s in students]
     return csv_response(course_id.to_deprecated_string().replace('/', '-') + '-anon-ids.csv', header, rows)
 
 

lms/djangoapps/instructor/views/legacy.py

@@ -691,8 +691,8 @@ def instructor_dashboard(request, course_id):
             courseenrollment__course_id=course_key,
         ).order_by('id')
 
-        datatable = {'header': ['User ID', 'Anonymized user ID', 'Course Specific Anonymized user ID']}
-        datatable['data'] = [[s.id, unique_id_for_user(s), anonymous_id_for_user(s, course_id)] for s in students]
+        datatable = {'header': ['User ID', 'Anonymized User ID', 'Course Specific Anonymized User ID']}
+        datatable['data'] = [[s.id, unique_id_for_user(s, save=False), anonymous_id_for_user(s, course_key, save=False)] for s in students]
         return return_csv(course_key.to_deprecated_string().replace('/', '-') + '-anon-ids.csv', datatable)
 
     #----------------------------------------