I want to add a ForeignKey field to my model. In order to achieve that, I did 3 steps:

  1. Added the ForeignKey field with null=True to my model, and then created a schemamigration.
  2. Created a datamigration in order to fill that foreign key with a sensible value. After this migration is applied, I'm pretty sure there is no object left with a NULL value at that field.
  3. Changed that ForeignKey field to null=False, and then created another schemamigration.

However, I'm having problems at the step 3:

? The field 'MyModel.fkfield' does not have a default specified, yet is NOT NULL.
? Since you are making this field non-nullable, you MUST specify a default
? value to use for existing rows. Would you like to:
?  1. Quit now, and add a default to the field in models.py
?  2. Specify a one-off value to use for existing columns now
? Please select a choice:

Well... No default value makes sense for this field, and also by now I'm pretty sure no object has that field as NULL. So... I don't know how to answer this question correctly. If I could, I would say "don't set any default value, and throw an error if you find any NULL in that column".

For now, as a workaround just to get over that question, I'm choosing option 2 and then using 1 as the one-off default value. This is a quite bad solution, but at least south doesn't complain about it and creates the migration.

  • What is the correct way of changing a field into NOT NULL? (using south)
  • What should I do when south asks me for a default value for a field that shouldn't have one?

I'm using django-1.2 and south-0.7.

Related question: django django-south

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