Django:非主键自动递增字段

Question

有没有一种可能的方法来创建像AutoField/BigAutoField这样的non primary-key auto incremented field，而又不容易失败(重复的ids，...)？

Answer 1

您可以使用信号创建一个，如下所示：

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

我们创建AutoFieldNonPrimary并使用一个自定义字段，如下所示

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)