UPD: change grace period for purging registration and participant data.

dav_events/workflow.py

@@ -3,6 +3,7 @@ import datetime
 import logging
 import re
 from django.apps import apps
+from django.db.models.functions import Length
 from django.utils import timezone
 from django.utils.translation import ugettext_lazy as _
 
@@ -286,8 +287,8 @@ class BasicWorkflow(object):
         qs = event.__class__.objects.filter(number__isnull=False,
                                             sport=event.sport,
                                             first_day__gte=year_begin,
-                                            first_day__lte=year_end).order_by('number')
-        last = qs.last()
+                                            first_day__lte=year_end).annotate(number_length=Length('number'))
+        last = qs.order_by('number_length', 'number').last()
         if last:
             match = re.match(r'^(?P<sport>[A-Z])(?P<count>[0-9][0-9]*)/(?P<year>[0-9][0-9]*)', last.number)
             if match: