Django: How to access original (unmodified) instance in post_save signal

Question

I want to do a data denormalization for better performance, and put a sum of votes my blog post receives inside Post model:

class Post(models.Model):
    \"\         


        

Answer 1

This is not an optimal solution, but it works.

@receiver(pre_save, sender=SomeModel)
def model_pre_save(sender, instance, **kwargs):
    try:
        instance._pre_save_instance = SomeModel.objects.get(pk=instance.pk)
    except SomeModel.DoesNotExist:
        instance._pre_save_instance = instance


@receiver(signal=post_save, sender=SomeModel)
def model_post_save(sender, instance, created, **kwargs):
    pre_save_instance = instance._pre_save_instance
    post_save_instance = instance