Re: South Error in migration:

On Wed, Mar 27, 2013 at 11:49 PM, Tim Cook <tim@mlhim.org> wrote:
> I can't find a similar scenario in the list archives, so .....
>
> I had run the initial migration, etc and all seemed fine.
>
> I modified one model from this:
> class CCD(models.Model):
> rm_version = models.ForeignKey(RMversion, related_name='%(class)s_related+')
> ...
>
> to this:
> class CCD(models.Model):
> prj_name = models.ForeignKey(Project, verbose_name="Project Name")
> ...
>
> The new ForeignKey in CCD, points to this, which already has the
> RMversion relation.
>
> class Project(models.Model):
> prj_name = models.CharField("project name", max_length=110, unique=True)
> rm_version = models.ForeignKey(RMversion, related_name='%(class)s_related+')
> owner_group = models.CharField(max_length=110) #must be a member
> of this group to edit this project
>
> During the migration, here are the prompts and my responses:
>

This should be many migrations, not one migration.

1) Schema migration: Add nullable foreign key to Project to CCD.
2) Data migration: Create Project objects as needed from 'RMversion' links
3) Data migration: Update CCD objects to point at projects
4) Schema migration: Drop RMversion foreign key from CCD
5) Schema migration: Make CCD->Project foreign key not null

Splitting it into multiple migration steps stops this from blowing up
in your face and preserves your data.

Cheers

Tom

--
You received this message because you are subscribed to the Google Groups "Django users" group.
To unsubscribe from this group and stop receiving emails from it, send an email to django-users+unsubscribe@googlegroups.com.
To post to this group, send email to django-users@googlegroups.com.
Visit this group at http://groups.google.com/group/django-users?hl=en.
For more options, visit https://groups.google.com/groups/opt_out.