Django unique, null and blank CharField giving 'already exists' error on Admin page

Question

I\'ve been getting the most weird error ever. I have a Person model

class Person(models.Model):
    user = models.OneToOneField(User, primary_key=True)
    f         


        

Answer 1

The root of the problem is that Django persist the empty value as empty-string, and not as null. To fix this, you can subclass CharField as follows:

class CharNullField(models.CharField):
    description = "CharField that stores NULL"

    def get_db_prep_value(self, value, connection=None, prepared=False):
        value = super(CharNullField, self).get_db_prep_value(value, connection, prepared)
        if value=="":
            return None
        else:
            return value

So get_db_prep_value will make it sure that null gets persisted