Django Many-to-many Query: Publications with no Articles? Publications with some Articles?

[Edward Sitarski]

I have read the Django Many to Many documentation.

Based on the example, I am stuck on how to formulate the following queries (this related to my "real life" problem):

1. What Publications have no Articles?
   
2. What Publications have at least one Article?

Doing it with a loop is straightforward:

publications_with_no_articles = [publication for publication in Publication.objects.all() if not publication.article_set.all().exists()]

publications_with_some_articles = [publication for publication in Publication.objects.all() if publication.article_set.all().exists()]

But, that's slow if you have a lot of publications - a query for each one.

Is there a way to formulate the queries with no loop, returning a QuerySet?

Apologies in advance if I am missing something simple...

[Shawn Milochik]

No articles:

Publication.objects.filter(article_set=None)

Has articles:

Publication.objects.exclude(article_set=None)

[Edward Sitarski]

Thanks - didn't see that one.

For my own reference/sanity, can you attach a link where this is documented?

I should have found this one before too.

[Shawn Milochik]

I couldn't find it in Django's documentation; just from StackOverflow and another source (both found via Google).

I always used to do something like Thing.objects.filter(other__id__isnull=True) to do that, but clearly this is better.