django-polymorphic

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Bert Constantin c2b420aea0 IMPORTANT: DB schema changed: Django's ContentType is now used instead of app-label and model-name (suggested by Ilya Semenov in issue 3). This is a cleaner and more efficient solution, and applabel/modelname are not stored redundantly in additional tables any more (the polymorphic models). This should be the final DB schema now (sorry for any inconvenience). Also some minor documentation updates.		2010-01-26 22:31:56 +01:00
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README.rst

===============================
Fully Polymorphic Django Models
===============================

News
----

* 	2010-1-26: IMPORTANT - database schema change (more info in change log).
	I hope I got this change in early enough before anyone started to use
	polymorphic.py in earnest. Sorry for any inconvenience.
	This should be the final DB schema now!


What is django_polymorphic good for?
------------------------------------

If ``ArtProject`` and ``ResearchProject`` inherit from the model ``Project``::

    >>> Project.objects.all()
	.
	[ <Project:         id 1, topic: "John's Gathering">,
	  <ArtProject:      id 2, topic: "Sculpting with Tim", artist: "T. Turner">,
	  <ResearchProject: id 3, topic: "Swallow Aerodynamics", supervisor: "Dr. Winter"> ]

In general, objects retrieved from the database are always delivered just as
they were created and saved, with the same type/class and fields. It doesn't
matter how you access these objects: be it through the model's own
managers/querysets, ForeignKey, ManyToMany or OneToOne fields.

The resulting querysets are polymorphic, and may deliver
objects of several different types in a single query result.

``django_polymorphic`` consists of just one add-on module, ``polymorphic.py``,
that adds this kind of automatic polymorphism to Django's model
inheritance system (for models that request this behaviour).

Please see additional examples and the documentation here:

	http://bserve.webhop.org/wiki/django_polymorphic

or in the DOCS.rst file in this repository.

Status
------

This module is still very experimental. Please see the docs for current restrictions,
caveats, and performance implications.