Avoid count(*) query in management command.

circle.yml

@@ -11,7 +11,7 @@ dependencies:
     - "pip install -r requirements.txt"
     - "pip install -r $VIRTUAL_ENV/src/xblock-sdk/requirements/base.txt"
     - "pip install -r $VIRTUAL_ENV/src/xblock-sdk/requirements/test.txt"
-    - "pip uninstall -y xblock-problem-builder && python setup.py sdist && pip install dist/xblock-problem-builder-2.6.8.tar.gz"
+    - "pip uninstall -y xblock-problem-builder && python setup.py sdist && pip install dist/xblock-problem-builder-2.6.9.tar.gz"
     - "pip install -r test_requirements.txt"
     - "mkdir var"
 test:

problem_builder/management/commands/copy_deprecated_course_id.py

@@ -1,4 +1,3 @@
-import math
 import time
 from django.core.management.base import BaseCommand
 from problem_builder.models import Answer
@@ -29,18 +28,21 @@ def handle(self, *args, **options):
         batch_size = options['batch_size']
         sleep_time = options['sleep']
         queryset = Answer.objects.filter(course_key__isnull=True)
-        batch_count = int(math.ceil(queryset.count() / float(batch_size)))
 
         self.stdout.write(
             "Copying Answer.course_id field into Answer.course_key in batches of {}".format(batch_size)
         )
 
-        for batch in xrange(1, batch_count + 1):
-            for answer in queryset[:batch_size]:
+        idx = 0
+        while True:
+            idx += 1
+            batch = queryset[:batch_size]
+            if not batch:
+                break
+            for answer in batch:
                 answer.course_key = answer.course_id
                 answer.save()
-            self.stdout.write("Processed batch {} of {}".format(batch, batch_count))
-            if batch != batch_count:
-                time.sleep(sleep_time)
+            self.stdout.write("Processed batch {}".format(idx))
+            time.sleep(sleep_time)
 
         self.stdout.write("Successfully copied Answer.course_id into Answer.course_key")

setup.py

@@ -71,7 +71,7 @@ def package_data(pkg, root_list):
 
 setup(
     name='xblock-problem-builder',
-    version='2.6.8',
+    version='2.6.9',
     description='XBlock - Problem Builder',
     packages=['problem_builder', 'problem_builder.v1'],
     install_requires=[