20130211

django.contrib.contenttypes and post_syncdb

Continued on https://www.lino-framework.org/tutorials/uiless.html.

The trick that disables the post_syncdb signal (https://www.lino-framework.org0209.html) works for django.contrib.auth and django.contrib.sites, but also has consequences for django.contrib.contenttypes. And contenttypes is being used on production data. So we must be careful.

Summary of tables that need special treatment in lino.utils.dumpy:

• ContentType objects don’t need to be stored in a dump because they can always be recreated.

• Site and Permission objects must be stored and must not be re-created

• Session can get lost in a dump and must not be stored.

Furthermore I perceive the –dumped command-line option as a useless complexification of the usage interface, and I had an idea how I can avoid it: we let the post_syncdb handlers do what they want, and then simply delete any automatically generated Site and Permission objects before restoring our dump. That’s done in lino.utils.dumpy.install_migrations().