#27627: OneToOneField doesn't allow multiple records with NULL value on
Microsoft
SQL Server
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Reporter: Ryan Schave | Owner: nobody
Type: Uncategorized | Status: new
Component: Uncategorized | Version:
Severity: Normal | Keywords:
Triage Stage: Unreviewed | Has patch: 0
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 0
UI/UX: 0 |
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A OneToOneField with null=True should allow multiple records to be saved
with a NULL value in the field. Consider the following models:
{{{
class Company(models.Model):
name = models.CharField(max_length=30)
class UserProfile(models.Model):
case_manager = models.BooleanField(default=False)
company = models.OneToOneField(Company, models.SET_NULL, blank=True,
null=True)
}}}
With a SQLite or PostgreSQL backend I'm able to save multiple records with
a NULL value:
{{{
up1 = UserProfile.objects.create(case_manager=True)
up2 = UserProfile.objects.create(case_manager=False)
}}}
With Microsoft SQL Server, the 2nd attempt to create a record with a NULL
value results in an integrity error:
django.db.utils.IntegrityError: ('23000', "[23000] [Microsoft][SQL Server
Native Client 11.0][SQL Server]Violation of UNIQUE KEY constraint
'UQ__contacts__3E2672343AF86B58'. Cannot insert duplicate key in object
'dbo.contacts_userprofile'. The duplicate key value is (<NULL>). (2627)
(SQLExecDirectW)")
This post - http://stackoverflow.com/a/767702 describes the problem and
suggests creating a "unique filtered index based on a predicate that
excludes NULLs".
I have confirmed that if I manually remove the constraint created by the
migration in the table schema and create a unique filtered index that
excludes NULLs on the company field I can create multiple records with a
NULL value in the company field. The migration should be adding a filter
to the index that looks something like:
{{{
WHERE ([company_id] IS NOT NULL)
}}}
I am able to duplicate the problem with Django 1.9.10 and 1.10.4.
--
Ticket URL: <https://code.djangoproject.com/ticket/27627>
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