问题
I'm trying to deal with a very puzzling error in a Django app. When DEBUG=False, trying to delete a user (via user.delete()) gives this database error:
DatabaseError: relation "social_auth_usersocialauth" does not exist
LINE 1: ...", "social_auth_usersocialauth"."extra_data" FROM "social_au...
However, I do not have social_auth or anything by a similar name in INSTALLED_APPS, nor are there any such tables in my database, nor does any of my code reference anything of the sort (I ran a text search on 'social' in the entire project folder) - and again, this works fine when DEBUG=True. social_auth is installed on my system and on my PYTHONPATH, but I cannot see where this app is getting the idea it should be having social_auth's tables in its database, let alone why it only thinks so when DEBUG=False.
What possible pathways could my app be getting this table from and how could I convince it it's not supposed to be there?
回答1:
The problem could be caused by saved generic relations realized by Django content types. Relations in Django are not only static, implemented by models and INSTALLED_APPS but also dynamic implemented by table django_content_type that saves mapping from a numeric id to app_label + model. An example of possible dynamic relationship is a permission or a comment. You can have or have not a permission to any table of any installed application. You can write a comment to everything e.g to an article, to a user to a comment itself without changing any model. This relation is realized by saving numeric id of ContentType related to that model (table) and a primary key of related object (row).
Django does not expect that someone can manipulate the database manually. If you use south for manipulation then if you after uninstalling an application then run syncdb, you are asked by south if you want automatically remove orphant content types. Then can be unused tables removed securely without beeing later referenced.
(Possible hack: delete from django_content_type where app_label='social_auth' but south is unfallible.)
Many parts of the question are still open.
Edit:
Why it was not the right way: All generic relations are from descendants to the parent and all data about the relation are saved in descendant. If the child app is removed from INSTALLED_APPS then django.db code can nevermore try to remove descendants because it can not recognize which columns contain the relation data.
回答2:
This table is created by django-social-auth application.
Looks like you've added it to your project and haven't launched migrate (or syncdb).
来源：https://stackoverflow.com/questions/13360251/django-database-error-missing-table-social-auth-usersocialauth-when-social-auth