Error on cascade deletion OneToOneField link with django-pyodbc backend

[Eugeny Klementev]

I have two models with OneToOne relation

class Unit (models.Model):

    label = models.CharField(max_length=32)

    datastream = models.OneToOneField ('Datastream', null=True, blank=True, related_name="unit")

    ...

class Datastream (models.Model):

    idd = models.AutoField(primary_key=True, auto_created=True, null=True)

    id = models.CharField(max_length=32)

    ...

During deletion of datastream these commands executed on DB server:

SQL: UPDATE "feeds_unit" SET "datastream_id" = NULL WHERE "id" IN (?, ?, ?)

PARAMS: (4, 5, 6)

SQL: DELETE FROM "feeds_unit" WHERE "id" IN (?, ?, ?)

PARAMS: (6, 5, 4)

I tried sqlite3 as backend - works fine.

But MSSQL raise error on "UPDATE "feeds_unit" SET "datastream_id" = NULL WHERE "id" IN (?, ?, ?)"

Error:

IntegrityError: ('23000', "[23000] [Microsoft][ODBC SQL Server Driver][SQL Server]Violation of UNIQU

E KEY constraint 'UQ__feeds_un__EAC1B8893E847883'. Cannot insert duplicate key in object 'dbo.feeds_

unit'. The duplicate key value is (<NULL>). (2627) (SQLExecDirectW); [01000] [Microsoft][ODBC SQL Se

rver Driver][SQL Server]The statement has been terminated. (3621)")

Can anybody help me?

[akaariai]

From the looks of it, it seems MSSQL isn't following the standard
regarding null equality in unique indexes. You might be interested in:
http://connect.microsoft.com/SQLServer/feedback/details/299229/change-unique-constraint-to-allow-multiple-null-values

Depending on your server version you might have a possibility to
define a filtered unique contraint. Otherwise, remove the constraint
in the database schema (the django model could still have the
OneToOneField for validation purposes) or alter your business logic in
a way that the referenced Unit models are also deleted.

- Anssi

On Feb 18, 9:38 pm, Eugeny Klementev <eugeny.klemen...@gmail.com>
wrote: