#28561: .order_by('foo__id') doesn't create a join
-------------------------------------+-------------------------------------
Reporter: Marten Kenbeek | Owner: nobody
Type: | Status: new
Cleanup/optimization |
Component: Documentation | Version: 1.11
Severity: Normal | Resolution:
Keywords: | Triage Stage:
| Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 1 | UI/UX: 0
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Description changed by Marten Kenbeek:
Old description:
> 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')
> > }}}
>
> 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
> }}}
New description:
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')
> }}}
([https://docs.djangoproject.com/en/1.11/ref/models/querysets/#order-by
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
}}}
--
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Ticket URL: <https://code.djangoproject.com/ticket/28561#comment:1>
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