Django - query filter on manytomany is exists

Question

I have such a model:

class News(models.Model):
    # ...
    channels = models.ManyToManyField(Channel)
    # ...

What is the most effective way to fetch news related to channels?

Answer 1

For a given channel, you can filter with:

News.object.filter(channels=my_channel)

for a collection (list, QuerySet, ...):

News.object.filter(channels__in=my_channel_collection)

For News objects that have at least one (or more) channels, we can query with:

News.objects.filter(channels__isnull=False).distinct()

or with .exclude(..):

News.objects.exclude(channels=None)