The Integrity error means that there is a row in the database with role = 1
So another row with role=1 would break the unique constraint and is not
allowed.
So either remove the unique constraint or make sure it will be unique.
Den tis 9 apr. 2019 13:29Ryan Jarvis <cabal...@gmail.com> skrev:
> Hey there,
>
> I'm trying out the new UniqueConstraint functionality in Django 2.2 and
> seem to be misunderstanding something. When adding a Constraint to the
> model I am getting an uncaught IntegrityError in the admin.
> I've got the following sample code:
>
> *models.py*
>
> class Seminar(models.Model):
> seminar_id = models.CharField(max_length=255, unique=True)
> members = models.ManyToManyField(User, through='SeminarRole',
> related_name="studies")
>
> class SeminarRole(models.Model):
> LEAD = 1 # Only 1 Lead permitted per seminar
> SUPPORT = 2
> ROLE_CHOICES = (
> (LEAD, 'Lead'),
> (SUPPORT, 'Support'),
> )
>
> user = models.ForeignKey(User, related_name='seminar_roles',
> on_delete=models.CASCADE)
> seminar = models.ForeignKey('seminar', related_name='roles',
> on_delete=models.CASCADE)
>
> role = models.IntegerField(choices=ROLE_CHOICES)
>
> class Meta:
> constraints = [
> models.UniqueConstraint(fields=['seminar'],
> condition=Q(role=1), name="only_one_lead"),
> ]
>
>
>
> For the code above in the Django Admin I can successfully add a
> SeminarRole with User1 as the Lead for SeminarA, User2 as the Lead for
> SeminarB, and User1 as Support for SeminarB but if I try and add User2 as
> another Lead to SeminarA it gives me an Exception. Should I be seeing the
> Django Admin catch this before hand?
>
> IntegrityError at /admin/study_management/seminarrole/add/
> duplicate key value violates unique constraint "only_one_lead"
> DETAIL: Key (seminar_id)=(1) already exists.
>
>
> I'm on Django 2.2, Python 3.7 and Postgres 11.2
>
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