+ # If NSD does not exist in DB, or it is not in use by any NS,
+ # validation is not required.
+ nsd = self.db.get_one("nsds", {"_id": descriptor_id}, fail_on_empty=False)
+ if not nsd or not detect_descriptor_usage(nsd, "nsds", self.db):
+ return
+
+ # Get the old and new descriptor contents in order to compare them.