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
15559	Distinct queries will cause errors with some custom model fields	urandom	nobody	"Starting with 1.3 rc1, some queries are marked as distinct by the system.

If a model now uses a custom field, that relies on a special DB column (like Postgresql's 'point' column),
the database will immediately throw an error, since such a column cannot be compared, and thus unique values cannot be found.

It would probably be a good idea to allow fields to specify whether they cannot be distinct:
custom = MyCustomField(distinctless=True)

which would turn this ordinary distinct query:
SELECT DISTINCT id, number, custom FROM foo;

into:
SELECT DISTINCT ON(id, number) FROM FOO;

Discussion link:
https://groups.google.com/forum/#!topic/django-developers/iO8z3iLpgg4"	Bug	new	Database layer (models, ORM)	dev	Normal			Michael Radziej	Accepted	0	0	0	0	0	0