Added flag to disable record change limit for update_index command

This limit makes sense for existing installations, but not so much for
new ones (e.g. a fresh devstack). This flag allows us to disable the
check as needed.

course_discovery/apps/edx_haystack_extensions/management/commands/update_index.py

@@ -13,6 +13,13 @@ logger = logging.getLogger(__name__)
 class Command(HaystackCommand):
     backends = []
 
+    def add_arguments(self, parser):
+        super().add_arguments(parser)
+        parser.add_argument(
+            '--disable-change-limit', action='store_true', dest='disable_change_limit',
+            help='Disables checks limiting the number of records modified.'
+        )
+
     def get_record_count(self, conn, index_name):
         return conn.count(index_name).get('count')
 
@@ -35,9 +42,13 @@ class Command(HaystackCommand):
 
         # Set the alias (from settings) to the timestamped catalog.
         for backend, index, alias in alias_mappings:
-            record_count_is_sane, index_info_string = self.sanity_check_new_index(backend.conn, index, record_count)
-            if not record_count_is_sane:
-                raise CommandError('Sanity check failed for new index. ' + index_info_string)
+            # Run a sanity check to ensure we aren't drastically changing the
+            # index, which could be indicative of a bug.
+            if not options.get('disable_change_limit', False):
+                record_count_is_sane, index_info_string = self.sanity_check_new_index(backend.conn, index, record_count)
+                if not record_count_is_sane:
+                    raise CommandError('Sanity check failed for new index. ' + index_info_string)
+
             self.set_alias(backend, alias, index)
 
     def percentage_change(self, current, previous):

course_discovery/apps/edx_haystack_extensions/tests/test_update_index.py

@@ -63,3 +63,11 @@ class UpdateIndexTests(ElasticsearchTestMixin, SearchIndexTestMixin, TestCase):
             with mock.patch('course_discovery.apps.edx_haystack_extensions.management.commands.'
                             'update_index.Command.get_record_count', return_value=record_count):
                 call_command('update_index')
+
+    @freeze_time('2016-06-21')
+    def test_sanity_check_disabled(self):
+        """ Verify the sanity check can be disabled. """
+        with mock.patch('course_discovery.apps.edx_haystack_extensions.management.commands.'
+                        'update_index.Command.sanity_check_new_index') as mock_sanity_check_new_index:
+            call_command('update_index', disable_change_limit=True)
+            self.assertFalse(mock_sanity_check_new_index.called)