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
16895	documentation should warn of cost of ordering	outofculture@…	Ivan Kolodyazhny	"In https://docs.djangoproject.com/en/dev/ref/models/options/#ordering it makes no mention of the database cost of ordering, especially for ordering on non-indexed fields, or the implicit joins of chained orderings.  (It doesn't even mention that it chains orderings!)  https://docs.djangoproject.com/en/dev/ref/models/querysets/#order-by is another location where the cost might be mentioned.  It could additionally go in https://docs.djangoproject.com/en/dev/topics/db/optimization/#don-t-retrieve-things-you-don-t-need as a hint for things to look for when optimizing.

Recommend for model options and querysets pages: ""Warning: Ordering is not a free operation.  Each field you add to the ordering will incur a cost from your database.  Each foreign key you add will include all of its default orderings implicitly.""

Recommend for optimization page: ""==Don't order if you don't care== Ordering is not free; each field added is an operation the database has to perform."""	Cleanup/optimization	closed	Documentation		Normal	fixed	afraid-to-commit		Accepted	1	1	0	0	0	0