migrate event table primary keys from integer to bigint

see: https://github.com/ansible/awx/issues/6010

awx/main/models/__init__.py

@@ -3,6 +3,7 @@
 
 # Django
 from django.conf import settings # noqa
+from django.db import connection, ProgrammingError
 from django.db.models.signals import pre_delete  # noqa
 
 # AWX
@@ -79,6 +80,27 @@ User.add_to_class('can_access_with_errors', check_user_access_with_errors)
 User.add_to_class('accessible_objects', user_accessible_objects)
 
 
+def enforce_bigint_pk_migration():
+    # see: https://github.com/ansible/awx/issues/6010
+    # look at all the event tables and verify that they have been fully migrated
+    # from the *old* int primary key table to the replacement bigint table
+    # if not, attempt to migrate them in the background
+    for tblname in (
+        'main_jobevent', 'main_inventoryupdateevent',
+        'main_projectupdateevent', 'main_adhoccommandevent',
+        'main_systemjobevent'
+    ):
+        with connection.cursor() as cursor:
+            try:
+                cursor.execute(f'SELECT MAX(id) FROM _old_{tblname}')
+                if cursor.fetchone():
+                    from awx.main.tasks import migrate_legacy_event_data
+                    migrate_legacy_event_data.apply_async([tblname])
+            except ProgrammingError:
+                # the table is gone (migration is unnecessary)
+                pass
+
+
 def cleanup_created_modified_by(sender, **kwargs):
     # work around a bug in django-polymorphic that doesn't properly
     # handle cascades for reverse foreign keys on the polymorphic base model