Pass South random unique default values when migrating

djangodjango-south

I am trying to forward migrate a model with existing data. The model has a new field with constraints unique=True and null=False.
When I do

./manage.py schemamigration myapp --auto

South lets me specify a default value for the new field by asking:

Specify a one-off value to use for existing columns now

Usually I set this to None but since this field needs to be unique I was wondering if it is possible to pass South a unique value via:

 >>> import uuid; uuid.uuid1().hex[0:35]

This gives me an error message 

! Invalid input: invalid syntax

Any ideas if it is possible to pass South random unique default values when migrating via the commandline?

Thanks.

Best Answer

Unfortunately only the datetime module is available for use as a one-off value in a schemamigration.

However, you can achieve the same effect by splitting this up into three migrations:

  • add new field to the model without constraints (with null=True, unique=False)
  • use a datamigration to add the UUID to the new field
  • add the constraint on the new field (with null=False, unique=True)

Tutorial on data migrations: http://south.readthedocs.org/en/0.7.6/tutorial/part3.html#data-migrations

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