Why is the number of users in the DB not the same as the number of User.pk? (Signals)?

Question

Django

I have a Customer model:

class Customer(models.Model):
    user = models.ForeignKey(User, verbose_name='Пользователь', on_delete=models.CASCADE, blank=True, null=True)
    avatar = models.ImageField("Аватар", blank=True, null=True)
    date = models.DateField("Дата создания", auto_now=True, auto_now_add=False, blank=True, null=True)
    id_num = models.PositiveIntegerField(verbose_name='id-номер', null=True, blank=True)

and also there is a function that, when saving a new user in User, adds id_num = User.pk to the attribute

@receiver(post_save, sender=User)
def created_user_profile(sender, instance, created, **kwargs):
    if created:
        Customer.objects.create(user=instance, id_num=instance.pk)


@receiver
def save_user_profile(sender, instance, **kwargs):
    instance.profile.save()

Why do I have 6 users in the database and when adding a new user to id_num = 76... and not 7?

Answer 1

Read about how auto- increment works in a database (or rather, a whole course / book on database and sql architecture).

Answer 2

If id_num means the client's serial number and it must be without gaps, then you definitely cannot use an id based on autoincrement for this, the order must be guaranteed on your own. A lot of people stepped on it, you're another.

Answer 3

Dr. Bacon , Yes, I'm aware, I wanted to make a binding by slug, but I don't know how, when adding, let's say from the username field to the slug field, the entered data from the user would be automatically translated into English characters.