[bump] Preventing JOIN while checking if a self referencing FK is null

[diafygi]

There is an old thread that didn't end in a resolution about
preventing joins in a filter(foreign_key=None) scenario.

http://groups.google.com/group/django-users/browse_thread/thread/61ee2fb22deae326

I'd like to bring it up again and ask if there is now a way to prevent
joins from a query.

An example:
class Blog(model.Models):
editor = models.ForeignKey(User, null=True)

# find all the blogs with no editors
>>> Blog.objects.filter(editor=None)
DEBUG:django.db.backends:(0.039) SELECT `myapp_blog`.`id` FROM
`myapp_blog` LEFT OUTER JOIN `myapp_user` ON (`myapp_blog`.`editor_id`
= `myapp_user`.`id`) WHERE `myapp_user`.`id` IS NULL;

# Is there a way to do this query?
>>> Blog.objects.filter(editor=None)
DEBUG:django.db.backends:(0.039) SELECT `myapp_blog`.`id` FROM
`myapp_blog` WHERE `myapp_blog`.`editor_id` IS NULL;

Thanks!
Daniel

[Javier Guerra Giraldez]

try:

> Blog.objects.filter(editor_id=None)

--
Javier

[diafygi]

>>> Blog.objects.filter(editor_id=None)
FieldError: Cannot resolve keyword 'editor_id' into field.

This was actually an offered answer in the previous thread, but the id
version of the field still raises a field error.

Daniel

On Mar 21, 9:47 am, Javier Guerra Giraldez <jav...@guerrag.com> wrote:
> try:
>
> > Blog.objects.filter(editor_id=None)
>
> --
> Javier

[Andre Terra]

On Wed, Mar 21, 2012 at 5:41 AM, diafygi <dia...@gmail.com> wrote:

>>> Blog.objects.filter(editor=None)

>>> print Blog.objects.filter(editor=None).values('id').query

SELECT "myapp_blog"."id" FROM "myapp_blog" WHERE "myappblog"."editor_id" IS NULL

Cheers,

AT

[Python_Junkie]

Use straight sql.

There are always potentially limitations with an abstraction such as the ORM.

Why try to fit a square peg into a round whole.

[Andre Terra]

Because django offers a nice ORM that makes it easy to do most queries, especially one-liners like this one.

And refactoring raw SQL is a royal PITA.

Cheers,

AT

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[diafygi]

I cannot confirm that behavior. Can others verify?

I'm using Django 1.3 and I get:
>>> print Blog.objects.filter(editor=None).values('id').query

SELECT `myapp_blog`.`id` FROM `myapp_blog` LEFT OUTER JOIN
`myapp_user` ON (`myapp_blog`.`editor_id` = `myapp_user`.`id`) WHERE
`myapp_user`.`id` IS NULL

-Daniel

On Mar 21, 2:07 pm, Andre Terra <andrete...@gmail.com> wrote:

[Andre Terra]

Sorry. In the process of changing model names to fit my own installation and test the code, I also managed to invert the relation.

Pay no attention to the man behind the curtains!

Cheers,
AT

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[diafygi]

Is there a reason why editor_id is meant to raise a field error?

-Daniel