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
26067	Orderable ArrayAgg and StringAgg	Floris den Hengst		"The [http://www.postgresql.org/docs/9.0/static/functions-aggregate.html documentation] of Postgres 9.0 first mentions the possibility of ordering the results within aggregations such as ARRAY_AGG and STRING_AGG.

This could be useful in some cases.
For example: it could make sense to perform a StringAgg in lexicographical order in some cases.

The basic format of ordering within aggregations in SQL is quite simple:
{{{
#!sql
SELECT ARRAY_AGG(some_field ORDER BY some_field ASC) FROM table;
SELECT ARRAY_AGG(some_field ORDER BY some_field DESC) FROM table;
SELECT ARRAY_AGG(some_field ORDER BY other_field ASC) FROM table;
}}}

It would be nice if the above would be supported as follows:
{{{
#!python
Model.objects.aggregate(ArrayAgg(some_field, order_by='some_field'))
Model.objects.aggregate(ArrayAgg(some_field, order_by='-some_field'))
Model.objects.aggregate(ArrayAgg(some_field, order_by='other_field'))
}}}

where order_by is an optional parameter. If it not specified, behavior can remain unchanged from the current implementation.

As noted by Josh Smeaton in the [https://groups.google.com/forum/#!topic/django-developers/YCSDX3GApBM mailinglist] discussion for this feature, any ordering added within '''may''' need to be contributed to GROUP BY. This might require some investigation."	New feature	new	contrib.postgres		Normal		ArrayAgg StringAgg ordering		Unreviewed	0	0	0	0	0	0