Django filter on related field using annotate

Question

I want to filter using annotate.

Here is my code:

class Blog(models.Model):
    name = models.CharField(max_length=100)

class Reader(models.Model):
    name = models.CharField(max_length=50)
    blog= models.ForeignKey(Blog)
    type = models.ForeignKey(ReaderType)

class ReaderType(models.Model):
    name = models.CharField(max_length=50)

I want to get all the blog's that has at least 2 Reader of type "male". I have this code to get the blogs that have at least 2 Readers:

Blog.objects.annotate(reader_count=Count(reader)).filter(reader_count__gte=2)

How do I add the part that filter only the blogs that have at least 2 readers that their type="male"

Andy Baker · Accepted Answer · 2016-03-06 15:31:59Z

4

You can just filter on the reader type directly in your query:

posts_with_multiple_readers = (
    Blog.objects.filter(reader__type__name='male')
    .annotate(reader_count=Count('reader'))
    .filter(reader_count__gte=2)
)

edited Mar 6, 2016 at 15:31

Andy Baker

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answered Jul 23, 2013 at 11:04

nitwit

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