django.db.utils.IntegrityError: FOREIGN KEY constraint failed

Question

My models.py

class Order(models.Model):
    user = models.ForeignKey(User, blank=True, null=True, on_delete=models.PROTECT)
    customer_email = models.EmailField(blank=True, null=True, default=None)
    customer_name = models.CharField(max_length = 64, blank=True, null=True, default=None)
    customer_phone = models.CharField(max_length = 48, blank=True, null=True, default=None)
    customer_address = models.CharField(max_length = 128, blank=True, null=True, default=None)
    total_price = models.DecimalField(max_digits=10, decimal_places=2, default=0) #total price for all products in order
    comments = models.TextField(blank=True, null=True, default=None)
    status = models.ForeignKey(Status, on_delete=models.PROTECT)
    created = models.DateTimeField(auto_now_add=True, auto_now=False)
    updated = models.DateTimeField(auto_now_add=False, auto_now=True)

    def __str__(self):
        return "Заказ %s %s" % (self.id, self.status.name)

    class Meta:
        verbose_name = "Заказ"
        verbose_name_plural = "Заказы"

    def save(self, *args, **kwargs):
        super(Order, self).save(*args, **kwargs)

My views.py.

def checkout(request):
    session_key = request.session.session_key
    products_in_basket = ProductInBasket.objects.filter(session_key=session_key, is_active=True)
    form = CheckoutContactForm(request.POST or None)
    if request.POST:
        print(request.POST)
        if form.is_valid():
            print("OK")
            data = request.POST
            name = data.get("name", "34343434")
            phone = data["phone"]
            user, created = User.objects.get_or_create(username=phone, defaults={"first_name": name})

            order = Order.objects.create(user=user, customer_name=name, customer_phone=phone, status_id=1)
            for name, value in data.items():
                if name.startswith("product_in_basket_"):
                    product_in_basket_id = name.split("product_in_basket_")[1]
                    product_in_basket = ProductInBasket.objects.get(id=product_in_basket_id)

                    product_in_basket.nmb = value
                    product_in_basket.order = order
                    product_in_basket.save(force_update=True)

                    ProductInOrder.objects.create(
                        product=product_in_basket.product, 
                        nmb=product_in_basket.nmb, 
                        price_per_item=product_in_basket.price_per_item, 
                        total_price=product_in_basket.total_price, 
                        order=order
                    )

        else:
            print("ERROR")
    return render(request, 'orders/checkout.html', locals())

The error:

Traceback (most recent call last):
  File "C:\Users\Nikita Shuliak\AppData\Local\Programs\Python\Python37- 
 32\lib\site-packages\django-2.1rc1-py3.7.egg\django\core\handlers\exception.py",   line 34, in inner
    response = get_response(request)
  File "C:\Users\Nikita Shuliak\AppData\Local\Programs\Python\Python37-32\lib\site-packages\django-2.1rc1-py3.7.egg\django\core\handlers\base.py", line 126, in _get_response
    response = self.process_exception_by_middleware(e, request)
  File "C:\Users\Nikita Shuliak\AppData\Local\Programs\Python\Python37-32\lib\site-packages\django-2.1rc1-py3.7.egg\django\core\handlers\base.py", line 124, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "C:\Users\Nikita Shuliak\Desktop\NJB\startup\orders\views.py", line 59, in checkout
    order = Order.objects.create(user=user, customer_name=name, customer_phone=phone, status_id=1)
  File "C:\Users\Nikita Shuliak\AppData\Local\Programs\Python\Python37-32\lib\site-packages\django-2.1rc1-py3.7.egg\django\db\utils.py", line 89, in __exit__
    raise dj_exc_value.with_traceback(traceback) from exc_value
  File "C:\Users\Nikita Shuliak\AppData\Local\Programs\Python\Python37-32\lib\site-packages\django-2.1rc1-py3.7.egg\django\db\backends\base\base.py", line 239, in _commit
    return self.connection.commit()
django.db.utils.IntegrityError: FOREIGN KEY constraint failed

STATUS MODEL EDDIT

Maybe problem is here. The problem is appeared after i added some code which you can see in comments. "This last error suggests that the Status with pk=1 already exists, but your previous error suggests the contrary. Please add your Status model to your question; lets see if there are any other conditions to consider.":

class Status(models.Model):
    name = models.CharField(max_length = 16, blank=True, null=True, default=None)
    is_active = models.BooleanField(default=True)
    created = models.DateTimeField(auto_now_add=True, auto_now=False)
    updated = models.DateTimeField(auto_now_add=False, auto_now=True)

    def __str__(self):
        return "Статус %s" % self.name

Solution 1

The error is in the line:

order = Order.objects.create(user=user, customer_name=name, customer_phone=phone, status_id=1)

You have to pass a status instance for the field status because it is a ForeignKey field. Just setting status_id to an integer won't work. I stand corrected, it can work; see this post.

Your error probably happens because either user (or user_id) or status (or status_id) are referencing instances that don't exist in the related database table.

Are you sure that there is a status with pk=1? Does the operation Status.objects.get(pk=1) succeed?

Solution 2

Try setting the named parameter of db_constraint of models.ForeignKey() to False(by default its True) like this:

status = models.ForeignKey(Status, on_delete=models.PROTECT,db_constraint=False)

This worked for me on a certain project the only issue will be that you will be unable to ensure the integrity of your db (e.g knowing whether all the Status objects referenced actually exist) but it makes sense if you're working with legacy code. Hope it helps.