Docs inaccurate about QuerySet.order_by('foo__id') creating a join

[Marten Kenbeek]

The documentation on order_by() states:

It is also possible to order a queryset by a related field, without incurring the cost of a JOIN, by referring to the _id of the related field:

# No Join
Entry.objects.order_by('blog_id')

# Join
Entry.objects.order_by('blog__id')

(​link)

However, in recent versions the latter query is optimised and won't create a join:

>>> print(Bar.objects.order_by('foo__id').query)
SELECT "foo_bar"."id", "foo_bar"."foo_id" FROM "foo_bar" ORDER BY "foo_bar"."foo_id" ASC

[Tim Graham]

I found that the behavior changed (removing the join for .order_by('blog__id')) in ccbba98131ace3beb43790c65e8f4eee94e9631c (Django 1.7). Oddly, the text in question was added in 21b858cb6735cdfdc695ff7b076e4cbc1981bc88 as part of Django 1.8, so it seems it was inaccurate since its introduction.

Unless there's a subtlety I'm not thinking of, I think we can remove that text. ​PR

[GitHub <noreply@…>]

In 44a6c27f:

Fixed #28561 -- Removed inaccurate docs about QuerySet.order_by() and joins.

As of ccbba98131ace3beb43790c65e8f4eee94e9631c, both examples don't use
a join.

[Tim Graham <timograham@…>]

In a86d9572:

[1.11.x] Fixed #28561 -- Removed inaccurate docs about QuerySet.order_by() and joins.

As of ccbba98131ace3beb43790c65e8f4eee94e9631c, both examples don't use
a join.

Backport of 44a6c27fd461e1d2f37388c26c629f8f170e8722 from master

[Tim Graham <timograham@…>]

In 260bc84:

[1.10.x] Fixed #28561 -- Removed inaccurate docs about QuerySet.order_by() and joins.

As of ccbba98131ace3beb43790c65e8f4eee94e9631c, both examples don't use
a join.

Backport of 44a6c27fd461e1d2f37388c26c629f8f170e8722 from master

[Tim Graham <timograham@…>]

In 3df8ccf6:

[1.9.x] Fixed #28561 -- Removed inaccurate docs about QuerySet.order_by() and joins.

As of ccbba98131ace3beb43790c65e8f4eee94e9631c, both examples don't use
a join.

Backport of 44a6c27fd461e1d2f37388c26c629f8f170e8722 from master

[Tim Graham <timograham@…>]

In e3cf8d2e:

[1.8.x] Fixed #28561 -- Removed inaccurate docs about QuerySet.order_by() and joins.

As of ccbba98131ace3beb43790c65e8f4eee94e9631c, both examples don't use
a join.

Backport of 44a6c27fd461e1d2f37388c26c629f8f170e8722 from master