Integrity Error django with UniqueConstraint - django

Question

I have the following model snippet:
class InvoiceReference(TemplateMixin, models.Model):
user = models.ForeignKey(
settings.AUTH_USER_MODEL,
on_delete=models.CASCADE,
)
reference_prefix = models.CharField(
max_length=100,
validators=(RegexValidator(regex='^\S+$',
message='reference prefix must not include spaces'),)
)
reference_offset = models.PositiveIntegerField(default=0)
reference_suffix = models.CharField(
max_length=100,
validators=(RegexValidator(regex='^\S+$',
message='reference suffix must not include spaces'),)
)
reference_separator = models.CharField(max_length=1)
class Meta:
constraints = [
models.UniqueConstraint(fields=('user', 'reference_prefix', 'reference_suffix', 'reference_separator',), name='unique_reference')
]
The idea is to have it so that a no single user cannot use the same reference_prefix, reference_separator and reference_suffix together multiple times. (if different users use the same combination of reference_prefix, reference_separator and reference_suffix this is ok.)
I am currently using the django-admin model form, where I have excluded the user field and attach a user in save_model:
class InvoiceReferenceAdmin(admin.ModelAdmin):
model = InvoiceReference
exclude = ('user',)
def save_model(self, request, obj, form, change):
if not obj.pk:
obj.user = request.user
super().save_model(request=request, obj=obj, form=form, change=change)
however, this results in an 'Integrity Error' when I try to save the model.
Traceback:
Traceback (most recent call last):
File "django/db/backends/utils.py", line 84, in _execute
return self.cursor.execute(sql, params)
File "django/db/backends/sqlite3/base.py", line 383, in execute
return Database.Cursor.execute(self, query, params)
sqlite3.IntegrityError: UNIQUE constraint failed: invoice_invoice.user_id, invoice_invoice.reference_prefix, invoice_invoice.reference_suffix, invoice_invoice.reference_separator
The above exception was the direct cause of the following exception:
Traceback (most recent call last):
File "django/core/handlers/exception.py", line 34, in inner
response = get_response(request)
File "django/core/handlers/base.py", line 115, in _get_response
response = self.process_exception_by_middleware(e, request)
File "django/core/handlers/base.py", line 113, in _get_response
response = wrapped_callback(request, *callback_args, **callback_kwargs)
File "django/contrib/admin/options.py", line 606, in wrapper
return self.admin_site.admin_view(view)(*args, **kwargs)
File "django/utils/decorators.py", line 142, in _wrapped_view
response = view_func(request, *args, **kwargs)
File "django/views/decorators/cache.py", line 44, in _wrapped_view_func
response = view_func(request, *args, **kwargs)
File "django/contrib/admin/sites.py", line 223, in inner
return view(request, *args, **kwargs)
File "django/contrib/admin/options.py", line 1645, in add_view
return self.changeform_view(request, None, form_url, extra_context)
File "django/utils/decorators.py", line 45, in _wrapper
return bound_method(*args, **kwargs)
File "django/utils/decorators.py", line 142, in _wrapped_view
response = view_func(request, *args, **kwargs)
File "django/contrib/admin/options.py", line 1529, in changeform_view
return self._changeform_view(request, object_id, form_url, extra_context)
File "django/contrib/admin/options.py", line 1572, in _changeform_view
self.save_model(request, new_object, form, not add)
File "/Users/leonhughes/dev/django/invoiceweb/invoice/admin.py", line 42, in save_model
super().save_model(request=request, obj=obj, form=form, change=change)
File "django/contrib/admin/options.py", line 1088, in save_model
obj.save()
File "django/db/models/base.py", line 741, in save
force_update=force_update, update_fields=update_fields)
File "django/db/models/base.py", line 779, in save_base
force_update, using, update_fields,
File "django/db/models/base.py", line 870, in _save_table
result = self._do_insert(cls._base_manager, using, fields, update_pk, raw)
File "django/db/models/base.py", line 908, in _do_insert
using=using, raw=raw)
File "django/db/models/manager.py", line 82, in manager_method
return getattr(self.get_queryset(), name)(*args, **kwargs)
File "django/db/models/query.py", line 1186, in _insert
return query.get_compiler(using=using).execute_sql(return_id)
File "django/db/models/sql/compiler.py", line 1375, in execute_sql
cursor.execute(sql, params)
File "django/db/backends/utils.py", line 99, in execute
return super().execute(sql, params)
File "django/db/backends/utils.py", line 67, in execute
return self._execute_with_wrappers(sql, params, many=False, executor=self._execute)
File "django/db/backends/utils.py", line 76, in _execute_with_wrappers
return executor(sql, params, many, context)
File "django/db/backends/utils.py", line 84, in _execute
return self.cursor.execute(sql, params)
File "django/db/utils.py", line 89, in __exit__
raise dj_exc_value.with_traceback(traceback) from exc_value
File "django/db/backends/utils.py", line 84, in _execute
return self.cursor.execute(sql, params)
File "django/db/backends/sqlite3/base.py", line 383, in execute
return Database.Cursor.execute(self, query, params)
django.db.utils.IntegrityError: UNIQUE constraint failed: invoice_invoice.user_id, invoice_invoice.reference_prefix, invoice_invoice.reference_suffix, invoice_invoice.reference_separator
I have seen this in the django documentation
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 without a condition (i.e. non-partial
unique constraints) 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.
As I have no conditions set shouldn't a ValidationError be raised first?

Answer 1

One way to achieve a similar result as yours would be to make user a hidden field in your admin form and then override ModelAdmin.get_changeform_initial_data to pass the current user as the value for this hidden input.
This would mean that the user would be included in unique validation checks as the field would not be excluded from the form. When editing an existing object initial data is ignored so you shouldn't override any existing user relation
class InvoiceReferenceAdminForm(forms.ModelForm):
class Meta:
model = InvoiceReference
fields = '__all__'
widgets = {'user': forms.HiddenInput}
class InvoiceReferenceAdmin(admin.ModelAdmin):
model = InvoiceReference
form = InvoiceReferenceAdminForm
def get_changeform_initial_data(self, request):
return {'user': request.user}