upgrade to partitions without a costly bulk data migration

keep pre-upgrade events in an old table (instead of a partition)

- instead of creating a default partition, keep all events in special
"unpartitioned" tables
- track these tables via distinct proxy=true models
- when generating the queryset for a UnifiedJob's events, look at the
  creation date of the job; if it's before the date of the migration,
  query on the old unpartitioned table, otherwise use the more modern table
  that provides auto-partitioning

awx/main/managers.py

@@ -11,11 +11,16 @@ from django.conf import settings
 from awx.main.utils.filters import SmartFilter
 from awx.main.utils.pglock import advisory_lock
 
-___all__ = ['HostManager', 'InstanceManager', 'InstanceGroupManager']
+___all__ = ['HostManager', 'InstanceManager', 'InstanceGroupManager', 'DeferJobCreatedManager']
 
 logger = logging.getLogger('awx.main.managers')
 
 
+class DeferJobCreatedManager(models.Manager):
+    def get_queryset(self):
+        return super(DeferJobCreatedManager, self).get_queryset().defer('job_created')
+
+
 class HostManager(models.Manager):
     """Custom manager class for Hosts model."""