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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