#37057: UniqueConstraint incorrectly raises ValidationError on nullable fields
in
condition
-------------------------------------+-------------------------------------
Reporter: Drews | Owner: (none)
Type: Bug | Status: new
Component: Database layer | Version: 6.0
(models, ORM) |
Severity: Normal | Resolution:
Keywords: UniqueConstraint | Triage Stage:
| Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
Description changed by Drews:
Old description:
> == Summary
> When a `UniqueConstraint` has a `condition` that references a nullable
> field (e.g., `condition=Q(cash_register_type=10)` on a nullable
> `PositiveSmallIntegerField`), Django's `UniqueConstraint.validate()`
> incorrectly reports a constraint violation if the instance being saved
> has `cash_register_type=None` and another record matching the condition
> already exists.
>
> ''Tested in Django==5.2.4 (with Postgres 17) and 6.0.4 (with Postgres
> 18)''
>
> == Steps to Reproduce
>
> {{{
> from django.db import models
>
> class Location(models.Model):
> name = models.CharField(max_length=100)
>
> class Device(models.Model):
> class CashRegisterType(models.IntegerChoices):
> MASTER = 10, "Master"
> SLAVE = 20, "Slave"
> name = models.CharField(max_length=100)
> pos_location = models.ForeignKey(Location, on_delete=models.CASCADE)
> cash_register_type = models.PositiveSmallIntegerField(
> choices=CashRegisterType,
> blank=True, null=True, default=None,
> )
>
> class Meta:
> constraints = [
> models.UniqueConstraint(
> fields=["pos_location"],
> condition=models.Q(cash_register_type=10),
> name="unique_master_cash_register",
> violation_error_message="Only one Master per
> POSLocation.",
> )
> ]
> }}}
>
> Create one Device with `cash_register_type` Master and creating another
> one for the same Location with `cash_register_type=None` will raise
> ValidationError
> {{{
> from myapp.models import Location, Device
>
> loc = Location.objects.create(name="Store 1")
>
> # 1. Create a Master -- works
> master = Device.objects.create(
> name="CashRegister A", pos_location=loc, cash_register_type=10
> )
>
> # 2. Create a second Device with cash_register_type=None
> # while a Master already exists -- BUG
> register_b = Device.objects.create(
> name="Device B", pos_location=loc, cash_register_type=None
> )
> }}}
>
> == Workaround
> Add an explicit `isnull=False` check to the condition:
> `condition=models.Q(cash_register_type=10) &
> models.Q(cash_register_type__isnull=False)`
> Although `10` should already be `isnull=False`.
New description:
== Summary
When a `UniqueConstraint` has a `condition` that references a nullable
field (e.g., `condition=Q(cash_register_type=10)` on a nullable
`PositiveSmallIntegerField`), Django's `UniqueConstraint.validate()`
incorrectly reports a constraint violation if the instance being saved has
`cash_register_type=None` and another record matching the condition
already exists.
''Tested in Django==5.2.4 (with Postgres 17) and 6.0.4 (with Postgres
18)''
== Steps to Reproduce
{{{
from django.db import models
class Location(models.Model):
name = models.CharField(max_length=100)
class Device(models.Model):
class CashRegisterType(models.IntegerChoices):
MASTER = 10, "Master"
SLAVE = 20, "Slave"
name = models.CharField(max_length=100)
pos_location = models.ForeignKey(Location, on_delete=models.CASCADE)
cash_register_type = models.PositiveSmallIntegerField(
choices=CashRegisterType,
blank=True, null=True, default=None,
)
class Meta:
constraints = [
models.UniqueConstraint(
fields=["pos_location"],
condition=models.Q(cash_register_type=10),
name="unique_master_cash_register",
violation_error_message="Only one Master per
POSLocation.",
)
]
}}}
Create one Device with `cash_register_type` Master and creating another
one for the same Location with `cash_register_type=None` will raise
ValidationError
{{{
from myapp.models import Location, Device
loc = Location.objects.create(name="Store 1")
# 1. Create a Master -- works
master = Device.objects.create(
name="CashRegister A", pos_location=loc, cash_register_type=10
)
# 2. Create a second Device with cash_register_type=None
# while a Master already exists -- BUG
register_b = Device(
name="Device B", pos_location=loc, cash_register_type=None
)
register_b.full_clean() # raises ValidationError
}}}
== Workaround
Add an explicit `isnull=False` check to the condition:
`condition=models.Q(cash_register_type=10) &
models.Q(cash_register_type__isnull=False)`
Although `10` should already be `isnull=False`.
--
--
Ticket URL: <https://code.djangoproject.com/ticket/37057#comment:4>
Django <https://code.djangoproject.com/>
The Web framework for perfectionists with deadlines.
--
You received this message because you are subscribed to the Google Groups
"Django updates" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
To view this discussion visit
https://groups.google.com/d/msgid/django-updates/0107019db5565f37-b7b9963e-d93c-4a94-8458-f9fb1fb9f16f-000000%40eu-central-1.amazonses.com.
