id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
10356	proxy models:  subclass a model without creating a new table	Ryan Kelly	Malcolm Tredinnick	"
Following a discussion with Malcolm on django-users, I've implemented support for what's tentatively named ""proxy models"".  These provide a way for model subclasses to modify the behaviour of a model without creating a new database table.  The canonical example seems to be subclassing the User model - you might want to add additional methods/managers/etc, but you still want to pull data directly from the main users table.  Under the attached patch this would look like the following:

{{{
    class MyUser(User)
        def extra_method(self):
            print ""I am a new method""
        class Meta:
            proxy = True
}}}

MyUser is now simply a different view onto the main User table, rather than a full-blown subclass with a separate table.

The main body of the patch is to db/models/base.py, where the meta attributes of proxy models are automatically set up.  Since it's now possible for a model to be using the same (table,primary key) pair as one of its base classes, I've added a small optimisation in db/models/sql/query.py that avoids a needless join in this case.  There's also some tests and a first stab at some documentation.

This patch also integrates with (but doesn't require) ticket #3163, by marking proxy models as unmanaged.

The django-users discussion leading to this patch can be found here:  http://groups.google.com/group/django-users/browse_thread/thread/fb06ff8e2a296f9c"		closed	Database layer (models, ORM)	1.0		fixed			Accepted	0	0	0	0	0	0