#1831 Add iter_related_changed method for getting related model.

core/change/decorator.py

 # ----------------------------------------------------------------------
 # @change decorator and worker
 # ----------------------------------------------------------------------
-# Copyright (C) 2007-2021 The NOC Project
+# Copyright (C) 2007-2022 The NOC Project
 # See LICENSE for details
 # ----------------------------------------------------------------------
 
@@ -79,6 +79,15 @@ def _on_document_delete(sender, document, *args, **kwargs):
         id=str(document.id),
         fields=None,
     )
+    if not hasattr(document, "get_changed_instance"):
+        return
+    document = document.get_changed_instance()
+    change_tracker.register(
+        op="update",
+        model=get_model_id(document),
+        id=str(document.id),
+        fields=None,
+    )
 
 
 def _on_model_change(sender, instance, created=False, *args, **kwargs):
@@ -121,3 +130,12 @@ def _on_model_delete(sender, instance, *args, **kwargs):
         id=str(instance.id),
         fields=None,
     )
+    if not hasattr(instance, "get_changed_instance"):
+        return
+    instance = instance.get_changed_instance()
+    change_tracker.register(
+        op="update",
+        model=get_model_id(instance),
+        id=str(instance.id),
+        fields=None,
+    )

dns/models/dnszonerecord.py

 # ---------------------------------------------------------------------
 # DNSZoneRecord model
 # ---------------------------------------------------------------------
-# Copyright (C) 2007-2020 The NOC Project
+# Copyright (C) 2007-2022 The NOC Project
 # See LICENSE for details
 # ---------------------------------------------------------------------
 
+# Python modules
+from typing import Optional
+
 # Third-party modules
 from django.db import models
 from django.contrib.postgres.fields import ArrayField
@@ -32,7 +35,7 @@ class DNSZoneRecord(NOCModel):
         db_table = "dns_dnszonerecord"
         app_label = "dns"
 
-    zone = models.ForeignKey(DNSZone, verbose_name="Zone", on_delete=models.CASCADE)
+    zone: "DNSZone" = models.ForeignKey(DNSZone, verbose_name="Zone", on_delete=models.CASCADE)
     name = models.CharField(_("Name"), max_length=64, blank=True, null=True)
     ttl = models.IntegerField(_("TTL"), null=True, blank=True)
     type = models.CharField(_("Type"), max_length=16)
@@ -50,7 +53,7 @@ class DNSZoneRecord(NOCModel):
         )
 
     @classmethod
-    def get_by_id(cls, id):
+    def get_by_id(cls, id) -> Optional["DNSZoneRecord"]:
         dnszonerecord = DNSZoneRecord.objects.filter(id=id)[:1]
         if dnszonerecord:
             return dnszonerecord[0]
@@ -60,5 +63,5 @@ class DNSZoneRecord(NOCModel):
         return self.zone
 
     @classmethod
-    def can_set_label(cls, label):
+    def can_set_label(cls, label: str) -> bool:
         return Label.get_effective_setting(label, setting="enable_dnszonerecord")