The code snippet below outlines the structure of my model:
class A():
foriegn_id1 = models.CharField # ref to a database not managed by django
foriegn_id2 = models.CharField
class B():
a = models.OneToOneField(A, on_delete=models.CASCADE)
I have implemented signals to ensure that when object B is deleted, object A is also deleted accordingly:
@receiver(post_delete, sender=B)
def post_delete_b(sender, instance, *args, **kwargs):
if instance.a:
instance.a.delete()
Furthermore, upon the deletion of object A, I want to trigger the removal of objects from unmanaged databases associated with it:
@receiver(post_delete, sender=A)
def post_delete_b(sender, instance, *args, **kwargs):
if instance.foriegn_id1:
delete_foriegn_obj_1(instance.foriegn_id1)
if instance.foriegn_id2:
delete_foriegn_obj_2(instance.foriegn_id2)
The issue arises when deleting object A, as Django's cascade deletion causes object B to also be deleted, triggering another post-delete signal. This results in a double call to delete_foriegn_obj, leading to failure during the second attempt.
To optimize performance, I considered verifying the existence of the object within delete_foriegn_obj, but this approach would necessitate additional database calls.
Hence, the question remains: Is there a method to determine within post_delete_b whether object A has been deleted? Both instance.a and A.objects.get(id=instance.a.id) currently return the object, indicating that Django caches the DB updates until all deletions are completed.