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I have an app with several django/python data models and associated postgres database tables. In this case the important ones are User and Feed.

I need to create a one to one relationship between a column in my Feed model and items in my User model. If I were starting the app from scratch I would simply define a user property in my Feed models as such:

from django.contrib.auth.models import User

class Feed(models.Model):
    ...
    user = models.OneToOneField(User)

Of course, being that my app is already functioning, I need to modify my database tables with SQL commands in accordance with my django/python data model changes.

My question is, what SQL commands do need to create a OneToOneField? I've used the documentation here: http://www.djangobook.com/en/2.0/chapter10.html as a guide when doing SQL commands in the past. But I'm concerned that I'm gonna screw something up when it comes to OneToOneFields.

The django manage.py sqlall command tells me that I need a column that looks like:

"user_id" integer NOT NULL UNIQUE REFERENCES "auth_user" ("id") DEFERRABLE INITIALLY DEFERRED
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Why not use a migration app? –  Ignacio Vazquez-Abrams Jun 25 '13 at 3:16
    
That of course requires me to configure the library and learn their API. I'm lazy, I want a one-time SQL command. But based on the lackluster response to this question, I'm thinking I might have to learn a migration app. Ive heard south is good. –  eblahm Jun 26 '13 at 14:54

1 Answer 1

up vote 0 down vote accepted

For all you out there with a similar problem... I ended up opting for the south migration library. (at some point I'd still like to learn SQL commands). Getting south to work was fairly straightforward.

$ pip install south
$ cd [pathtoproject]
$ vim [project]/settings.py

# make sure the following is reflected
INSTALLED_APPS += ('south',) 

$ ./manage.py syncdb
$ ./manage.py convert_to_south [myapp]
$ vim [myapp]/models.py

# make the changes to the data models. 
# south has to be initialized before these changes occur

class Feed(models.Model):
    ...
    user = models.OneToOneField(User)


$ ./manage.py schemamigration [myapp] --auto
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