Yeah, this one just bit me in the Django Admin as well. According to the docs <https://docs.djangoproject.com/en/2.2/ref/models/constraints/>,
Validation of Constraints > > In general constraints are *not* checked during full_clean(), and do not > raise ValidationErrors. Rather you’ll get a database integrity error on > save(). UniqueConstraints are different in this regard, in that they > leverage the existing validate_unique() logic, and thus enable two-stage > validation. In addition to IntegrityError on save(), ValidationError is > also raised during model validation when the UniqueConstraint is violated. > However, it makes no mention of UniqueConstraint instances with conditions being ignored. It took me diving into the Django source code to find out what was happening. Thankfully, I stumbled upon this here to confirm my sanity. :) On Tuesday, April 9, 2019 at 9:13:19 AM UTC-4, Simon Charette wrote: > > No form validation is implemented for UniqueConstraint(condition) yet as > that would require > a non-trivial refactor of how it's performed. It was discussed during the > feature development[0]. > > I'd suggest you override you form or your model's clean() method to > perform the validation > yourself until built-in support is added. > > Submitting a new Trac ticket so we don't loose track of the issue would > also be appreciated. > > Cheers, > Simon > > [0] https://github.com/django/django/pull/10796#discussion_r244216763 > > Le mardi 9 avril 2019 07:29:53 UTC-4, Ryan Jarvis a écrit : >> >> 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 >> >> -- You received this message because you are subscribed to the Google Groups "Django users" group. To unsubscribe from this group and stop receiving emails from it, send an email to django-users+unsubscr...@googlegroups.com. To post to this group, send email to django-users@googlegroups.com. Visit this group at https://groups.google.com/group/django-users. To view this discussion on the web visit https://groups.google.com/d/msgid/django-users/e0a79eab-e9d6-46fb-86c3-8f5d97fb3f7c%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
