fix: compare emails case-insensitively when setting assignment lms_us…

…er_ids

ENT-8129 | The email stored on assignment records might be only a case-insensitive
match to the corresponding email in the core.User records, so do case-insensitive
matching during the assignment flow and during the post-user-save signal
that updates assignment ``lms_user_ids``.

enterprise_access/apps/content_assignments/api.py

@@ -8,7 +8,8 @@
 from typing import Iterable
 
 from django.db import transaction
-from django.db.models import Sum
+from django.db.models import Q, Sum
+from django.db.models.functions import Lower
 from opaque_keys import InvalidKeyError
 from opaque_keys.edx.keys import CourseKey
 from opaque_keys.edx.locator import CourseLocator
@@ -33,7 +34,7 @@
 #   * Divide result by 10 in case we are off by an order of magnitude.
 #
 # Batch size derivation formula: ((1 MB) / (258 B)) / 10 ≈ 350
-USER_EMAIL_READ_BATCH_SIZE = 350
+USER_EMAIL_READ_BATCH_SIZE = 100
 
 
 class AllocationException(Exception):
@@ -392,14 +393,22 @@ def _try_populate_assignments_lms_user_id(assignments):
     for assignment_chunk in chunks(assignments_with_empty_lms_user_id, USER_EMAIL_READ_BATCH_SIZE):
         emails = [assignment.learner_email for assignment in assignment_chunk]
         # Construct a list of tuples containing (email, lms_user_id) for every assignment in this chunk.
-        email_lms_user_id = User.objects.filter(
-            email__in=emails,  # this is the part that could exceed max statement length if batch size is too large.
-            lms_user_id__isnull=False,
-        ).values_list('email', 'lms_user_id')
+        # this is the part that could exceed max statement length if batch size is too large.
+        # There's no case-insensitive IN query in Django, so we have to build up a big
+        # OR type of query.
+        email_filter = Q()
+        for assignment_email in emails:
+            email_filter |= Q(email__iexact=assignment_email)
+
+        email_lms_user_id = User.objects.filter(email_filter, lms_user_id__isnull=False).annotate(
+            email_lower=Lower('email'),
+        ).values_list('email_lower', 'lms_user_id')
+
         # dict() on a list of 2-tuples treats the first elements as keys and second elements as values.
         lms_user_id_by_email = dict(email_lms_user_id)
+
         for assignment in assignment_chunk:
-            lms_user_id = lms_user_id_by_email.get(assignment.learner_email)
+            lms_user_id = lms_user_id_by_email.get(assignment.learner_email.lower())
             if lms_user_id:
                 assignment.lms_user_id = lms_user_id
                 assignments_to_save.append(assignment)

enterprise_access/apps/content_assignments/signals.py

@@ -20,7 +20,7 @@ def update_assignment_lms_user_id_from_user_email(sender, **kwargs):  # pylint:
     user = kwargs['instance']
     if user.lms_user_id:
         assignments_to_update = LearnerContentAssignment.objects.filter(
-            learner_email=user.email,
+            learner_email__iexact=user.email,
             lms_user_id=None,
         )
 

enterprise_access/apps/content_assignments/tests/test_api.py

@@ -467,7 +467,7 @@ def test_allocate_assignments_set_lms_user_id(
         }
 
         if user_exists:
-            UserFactory(username='alice', email=learner_email, lms_user_id=lms_user_id)
+            UserFactory(username='alice', email=learner_email.upper(), lms_user_id=lms_user_id)
 
         assignment = None
         if existing_assignment_state:

enterprise_access/apps/content_assignments/tests/test_signals.py

@@ -41,8 +41,8 @@ def test_update_assignment_lms_user_id_from_user_email_login(self):
         test_user = UserFactory(email=TEST_EMAIL)
         # Simulate creating asignments for the test learner AFTER user creation.
         assignments_post_register = [
-            LearnerContentAssignmentFactory(learner_email=TEST_EMAIL, lms_user_id=None),
-            LearnerContentAssignmentFactory(learner_email=TEST_EMAIL, lms_user_id=None),
+            LearnerContentAssignmentFactory(learner_email=TEST_EMAIL.upper(), lms_user_id=None),
+            LearnerContentAssignmentFactory(learner_email=TEST_EMAIL.upper(), lms_user_id=None),
         ]
         # Simulate the learner logging in.
         test_user.last_login = timezone.now()