Django: non primary-key auto incremented field

Question

is there a possible way to create a non primary-key auto incremented field like a AutoField/BigAutoField that is not prone to failure(duplicated ids, ...) ?

Answer 1

You can use the post_save signal to create one, like this:

from django.db.models.signals import post_save
from django.dispatch import receiver

class YourModel(models.Model):
   auto_field = models.BigIntegerField(null=True, default=None)

@receiver(post_save, sender=YourModel)
def update_auto_field(sender, instance, created, **kwargs):
    if created:
        instance.auto_field = instance.pk
        instance.save()

Answer 2

We create AutoFieldNonPrimary and use a custom field like below

from django.db.models.fields import AutoField
from django.db.models.fields import checks


class AutoFieldNonPrimary(AutoField):

    def _check_primary_key(self):
        if self.primary_key:
            return [
                checks.Error(
                    "AutoFieldNonPrimary must not set primary_key=True.",
                    obj=self,
                    id="fields.E100",
                )
            ]
        else:
            return []

class YourModel(models.Model):
   auto_field = models.AutoFieldNonPrimary(primary_key=False)