Usage of unique_for_date

Question

I'm trying to use unique_for_date option to prevent creating multiple posts with the same slug for the same date. But it doesn't seem to work at all: I still can create posts with the same slug from the shell and admin dashboard. The same goes for ModelForm. My models.py:

class Post(models.Model):

    STATUS_CHOICES = (
        ('draft', 'Draft'),
        ('published', 'Published'),
        ('suspended', 'Suspended'),
    )

    title = models.CharField(max_length=200)
    slug = models.SlugField(max_length=200, unique_for_date='created')
    status = models.CharField(max_length=15,
                              choices=STATUS_CHOICES,
                              default='draft')
    content = models.TextField(max_length=200000, blank=True)
    # dates
    created = models.DateTimeField(auto_now_add=True)
    updated = models.DateTimeField(auto_now=True)
    publish = models.DateTimeField(default=timezone.now)

I've found some kind of a workaround for problem by changing auto_now_add=True to default=timezone.now but it only shows error while creating object via django admin - still no errors while creating objects from shell or form.

Update: I know that using auto_now_add sets editable=False causing django to skip field validation, but it doesn't explain why it skips validation even with default=timezone.now

Update 2: For some reason unique_for_date works only for django-admin dashboard forms (in my case at least). To get the same effect for other forms I've overridden the clean_fields method of the model (forces django to validate unique fields):

def clean_fields(self, exclude=None):
    super().clean_fields(exclude=exclude)
    self.validate_unique()

Answer 1

I think that you are having created as DateTimeField , so it is considering time also. Try changing it to DateField

Answer 2

The unique_for_date constraint is enforced at the Django admin-form level but not at the database level. If you look at the docs,

This is enforced by Model.validate_unique() during model validation but not at the database level. If any unique_for_date constraint involves fields that are not part of a ModelForm (for example, if one of the fields is listed in exclude or has editable=False), Model.validate_unique() will skip validation for that particular constraint.

If you need to enforce a database level unique constraint, then I may suggest adding a unique_together constraint in your Meta class. Also, you may need to change your created field to a DateField(), if you may consider.