Remove temporary transition code.

Now that all data has been migrated to the new course_key column, we can
remove the temporary transition code.

problem_builder/answer.py

@@ -23,11 +23,6 @@
 import logging
 from lazy import lazy
 
-from django.core.exceptions import ValidationError
-from django.db import IntegrityError
-from django.db.models import Q
-from django.utils.crypto import get_random_string
-
 from .models import Answer
 
 from xblock.core import XBlock
@@ -69,35 +64,6 @@ class AnswerMixin(XBlockWithPreviewMixin, XBlockWithTranslationServiceMixin):
         except AttributeError:
             return self.scope_ids.user_id
 
-    @staticmethod
-    def _fetch_model_object(name, student_id, course_id):
-        answer = Answer.objects.get(
-            Q(name=name),
-            Q(student_id=student_id),
-            Q(course_key=course_id) | Q(course_id=course_id)
-        )
-        if not answer.course_key:
-            answer.course_key = answer.course_id
-        return answer
-
-    @staticmethod
-    def _create_model_object(name, student_id, course_id):
-        # Try to store the course_id into the deprecated course_id field if it fits into
-        # the 50 character limit for compatibility with old code. If it does not fit,
-        # use a random temporary value until the column gets removed in next release.
-        # This should not create any issues with old code running alongside the new code,
-        # since Answer blocks don't work with old code when course_id is longer than 50 chars anyway.
-        if len(course_id) > 50:
-            # The deprecated course_id field cannot be blank. It also needs to be unique together with
-            # the name and student_id fields, so we cannot use a static placeholder value, we generate
-            # a random value instead, to make the database happy.
-            deprecated_course_id = get_random_string(24)
-        else:
-            deprecated_course_id = course_id
-        answer = Answer(student_id=student_id, name=name, course_key=course_id, course_id=deprecated_course_id)
-        answer.save()
-        return answer
-
     def get_model_object(self, name=None):
         """
         Fetches the Answer model object for the answer named `name`
@@ -110,18 +76,13 @@ class AnswerMixin(XBlockWithPreviewMixin, XBlockWithTranslationServiceMixin):
             raise ValueError('AnswerBlock.name field need to be set to a non-null/empty value')
 
         student_id = self._get_student_id()
-        course_id = self._get_course_id()
+        course_key = self._get_course_id()
 
-        try:
-            answer_data = self._fetch_model_object(name, student_id, course_id)
-        except Answer.DoesNotExist:
-            try:
-                # Answer object does not exist, try to create it.
-                answer_data = self._create_model_object(name, student_id, course_id)
-            except (IntegrityError, ValidationError):
-                # Integrity/validation error means the object must have been created in the meantime,
-                # so fetch the new object from the db.
-                answer_data = self._fetch_model_object(name, student_id, course_id)
+        answer_data, _ = Answer.objects.get_or_create(
+            student_id=student_id,
+            course_key=course_key,
+            name=name,
+        )
 
         return answer_data
 

problem_builder/models.py

@@ -43,7 +43,7 @@ class Answer(models.Model):
     name = models.CharField(max_length=50, db_index=True)
     student_id = models.CharField(max_length=32, db_index=True)
     # course_id is deprecated; it will be removed in next release.
-    course_id = models.CharField(max_length=50, db_index=True, null=True, default=None)
+    course_id = models.CharField(max_length=50, db_index=True, blank=True, null=True, default=None)
     # course_key is the new course_id replacement with extended max_length.
     course_key = models.CharField(max_length=255, db_index=True)
     student_input = models.TextField(blank=True, default='')

problem_builder/tests/unit/test_answer_mixin.py

 """
-Tests temporary AnswerMixin code that helps migrate course_id column to course_key.
+Unit tests for AnswerMixin.
 """
 import unittest
 from collections import namedtuple
 from django.utils.crypto import get_random_string
-from mock import patch
 
 from problem_builder.answer import AnswerMixin
 from problem_builder.models import Answer
@@ -37,7 +36,6 @@ class TestAnswerMixin(unittest.TestCase):
         model = answer_mixin.get_model_object()
         self.assertEqual(model.name, name)
         self.assertEqual(model.student_id, self.anonymous_student_id)
-        self.assertEqual(model.course_id, self.course_id)
         self.assertEqual(model.course_key, self.course_id)
         self.assertEqual(Answer.objects.get(pk=model.pk), model)
 
@@ -47,29 +45,12 @@ class TestAnswerMixin(unittest.TestCase):
             name=name,
             student_id=self.anonymous_student_id,
             course_key=self.course_id,
-            course_id='ignored'
         )
         existing_model.save()
         answer_mixin = self.make_answer_mixin(name=name)
         model = answer_mixin.get_model_object()
         self.assertEqual(model, existing_model)
 
-    def test_finds_instance_by_course_id(self):
-        name = 'test-course-id'
-        existing_model = Answer(
-            name=name,
-            student_id=self.anonymous_student_id,
-            course_id=self.course_id,
-            course_key=None
-        )
-        # Temporarily patch full_clean to allow saving object with blank course_key to the database.
-        with patch.object(Answer, 'full_clean', return_value=None):
-            existing_model.save()
-        answer_mixin = self.make_answer_mixin(name=name)
-        model = answer_mixin.get_model_object()
-        self.assertEqual(model, existing_model)
-        self.assertEqual(model.course_key, self.course_id)
-
     def test_works_with_long_course_keys(self):
         course_id = 'course-v1:VeryLongOrganizationName+VeryLongCourseNumber+VeryLongCourseRun'
         self.assertTrue(len(course_id) > 50)  # precondition check