Problems with contenttypes when loading a fixture in Django

Question

I am having trouble loading Django fixtures into my MySQL database because of contenttypes conflicts. First I tried dumping the data from only my app like this:

./manage.py dumpdata escola > fixture.json

but I kept getting missing foreign key problems, because my app "escola" uses tables from other applications. I kept adding additional apps until I got to this:

./manage.py dumpdata contenttypes auth escola > fixture.json

Now the problem is the following constraint violation when I try to load the data as a test fixture:

IntegrityError: (1062, "Duplicate entry 'escola-t23aluno' for key 2")

It seems the problem is that Django is trying to dynamically recreate contenttypes with different primary key values that conflict with the primary key values from the fixture. This appears to be the same as bug documented here: http://code.djangoproject.com/ticket/7052

The problem is that the recommended workaround is to dump the contenttypes app which I'm already doing!? What gives? If it makes any difference I do have some custom model permissions as documented here: http://docs.djangoproject.com/en/dev/ref/models/options/#permissions

Answer 1

manage.py dumpdata --natural will use a more durable representation of foreign keys. In django they are called "natural keys". For example:

• Permission.codename is used in favour of Permission.id
• User.username is used in favour of User.id

Read more: natural keys section in "serializing django objects"

Some other useful arguments for dumpdata:

• --indent=4 make it human readable.
• -e sessions exclude session data
• -e admin exclude history of admin actions on admin site
• -e contenttypes -e auth.Permission exclude objects which are recreated automatically from schema every time during syncdb. Only use it together with --natural or else you might end up with badly aligned id numbers.