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
26115	Admin list sort using callable, latest, and admin_order_field causes duplicates.	Kevin Mann	nobody	"In a data model that records changes over time to the way two entities relate, I am able to correctly display the latest record in an admin list by creating a callable using `latest()`. However, when sorting the column, if there is more than one record related to the admin list parent record, the number of rows will increase to that number, showing duplicates.

Example:

Given: A class `Employee` and a class `Title`, with a class `EmployeeTitle` that joins the two with `start_date` and `end_date` fields.

I'd like to show the employee's current title on the admin page, and be able to sort by that column. I create a callable `current_title()` in the `Employee` class which returns the latest of the `employeetitle_set` based on `start_date`.

I set the admin order field to be `'employeetitle__title__name'`.

If the employee has been more than one title the unsorted list displays correctly, but the list sorted by `current_title` shows duplicates where all the titles show the same current title.

The expected behavior is that there is a single list entry for each employee and the list is sorted by the `current_title`.

I'm attaching a simple models.py and admin.py for reference."	Bug	closed	contrib.admin	1.9	Normal	duplicate	admin, sort, admin_order_field, list_display callable		Unreviewed	0	0	0	0	0	0