On May 23, 2:36 pm, bruno desthuilliers
<bruno.desthuilli...@gmail.com> wrote:
> > The interaction between
> > multiple references to same reverse foreign key relation in single
> > queryset is somewhat hard to remember. Could you post the generated
> > SQL?
>
> here you go - reformated for readability:
>
> SELECT
> `blookcore_category`.`id`,
> `blookcore_category`.`label`
> FROM
> `blookcore_category`
> LEFT OUTER JOIN `blookcore_classification`
> ON (`blookcore_category`.`id` =
> `blookcore_classification`.`category_id`)
> WHERE
> `blookcore_classification`.`blook_id` = 118
> ORDER BY
> `blookcore_classification`.`position` ASC
>
> I don't quite get why it uses a left outer join instead of the inner
> join used when not adding the order by clause, but writing a working,
> usable ORM is not exactly a piece of cake so I won't complain about
> this ;). Anyway: the where clause still makes sure we only get the
> relevant categories.
Right you are about the query producing correct results. I should have
checked that myself.
I guess (again!) that the reason for the LEFT JOIN is this call in sql/
compiler.py:_setup_joins()
self.query.promote_alias_chain(joins,
self.query.alias_map[joins[0]].join_type == self.query.LOUTER)
This seems to promote the join to outer join too aggressively, the
promote_alias_chain call does not see that the join is constrained by
other conditions already. I don't know if this has any practical
effects, nor do I know how easy/hard this would be to fix. It could be
as easy as just starting from the first new join generated by the
_setup_joins() call, and leaving the pre-existing joins alone. If it
is that easy, it should be fixed...
- Anssi
--
You received this message because you are subscribed to the Google Groups
"Django users" group.
To post to this group, send email to django-users@googlegroups.com.
To unsubscribe from this group, send email to
django-users+unsubscr...@googlegroups.com.
For more options, visit this group at
http://groups.google.com/group/django-users?hl=en.
