related_query_name - what is it?

[Petr Glotov]

Django doc says:

 ForeignKey.related_query_name

New in Django 1.6.

The name to use for the reverse filter name from the target model. Defaults to the value of related_name if it is set, otherwise it defaults to the name of the model:

# Declare the ForeignKey with related_query_name

class Tag(models.Model):

    article = models.ForeignKey(Article, related_name="tags", related_query_name="tag")

    name = models.CharField(max_length=255)

# That's now the name of the reverse filter

article_instance.filter(tag__name="important")

However, an object model doesn't have filter() method. I am trying to use related_query_name to filter a model M with a condition on the related objects R. The problem is that result includes instances of M which don't have related objects in R. But I would like to first understand what related_query_name is. Could someone explain? Thanks,

Petr

[Petr Glotov]

Correction: first sentence of the question should read:

However, a model instance doesn't have filter() method. 

[Simon Charette]

The documentation is wrong, it should be:

# That's now the name of the reverse filter

Article.objects.filter(tag__name="important")

I'll commit a documentation admonition and give you credit.

Thanks for spotting this!

[Petr Glotov]

No problem.

I think I also found how to deal with M instances which are not related to R (R instances have foreign key to M). I tried M.filter(related_query_name_from_R__isnull=False) and it seems to work.