FOREIGN KEY constraint failed delete django

Question

Sorry for my english. I spend 2 days but cant understand why i have error:

FOREIGN KEY constraint failed

I use python 2.7 everything works fine, then i update to python 3.5.2 and now when i try delete i have this error. I have models as below:

class Auction(models.Model):
    sealers = models.ForeignKey(User, related_name="sealers", on_delete=models.CASCADE)
    buyer = models.ManyToManyField(User, related_name='buyer')
    product_in_auction = models.ForeignKey(Product, related_name='product_in_auction', null=True, blank=True, on_delete=models.CASCADE)
    name_auction = models.CharField(max_length=64, blank=False, null=False)
    description = models.TextField(blank=True, null=True, default=None)
    conf_propose = models.OneToOneField('Propose', null=True, blank=True, related_name='confirm_proposition', on_delete=models.CASCADE)
    created_at = models.DateTimeField(auto_now_add=True, auto_now=False)
    updated_at = models.DateTimeField(auto_now_add=False, auto_now=True)

    class Meta:
        verbose_name = 'Auction'
        verbose_name_plural = 'Auctions'

    def __str__(self):
        return "%s" % (self.name_auction)


class Propose(models.Model):
    buyer = models.ForeignKey(User, related_name="propositions_of_auction", on_delete=models.CASCADE, null=True, blank=True)
    auction = models.ForeignKey(Auction, related_name="propositions_of_auction", on_delete=models.CASCADE)
    bit = models.DecimalField(max_digits=10, decimal_places=2, default=0, blank=True)
    created_at = models.DateTimeField(auto_now_add=True, auto_now=False)
    updated_at = models.DateTimeField(auto_now_add=False, auto_now=True)

    class Meta:
        verbose_name = 'Proposition of the auction'
        verbose_name_plural = 'Propositions of the auction'

    def __str__(self):
        return "%s" % (self.bit)

When i try delete some auction i have error

FOREIGN KEY constraint failed

Answer 1

I don't think the problem is about the python version. Just like the error says, you have Foreign key constraint. So in your Propose model you have a field called auction which is the ForeignKey of model Auction, So if you want to delete some auction instance it will affect the data in the table Propose as well.

Answer 2

I had this error every time I wanted to change something using administration. I was lucky not to have a big database. So I simply deleted all migrations (except __init__.py ), the database and made them again using manage.py makemigrations and manage.py migrate . This straightforward method worked for me!