Django: How to add counts of non-related object? - sql

Question

I have two indirectly related tables - Posts and Follower_to_followee
models.py:
class Post(models.Model):
auth_user = models.ForeignKey(User, null=True, blank=True, verbose_name='Author', help_text="Author")
title = models.CharField(blank=True, max_length=255, help_text="Post Title")
post_content = models.TextField (help_text="Post Content")
class Follower_to_followee(models.Model):
follower = models.ForeignKey(User, related_name='user_followers', null=True, blank=True, help_text="Follower")
followee = models.ForeignKey(User, related_name='user_followees', null=True, blank=True, help_text="Followee")
The folowee is indirectly related to post auth_user (post author) in posts. It is, though, directly related to Django user table and user table is directly related to post table.
How can I select all followees for a specific follower and include post counts for each followee in the result of the query without involving the user table? Actually, at this point I am not even clear how to do that involving the user table. Please help.

Answer 1

It's possible to write query generating single SQL, try something like
qs = User.objects.filter(user_followees__follower=specific_follower).annotate(
post_count=models.Count('post'))
for u in qs:
print u, u.post_count
Check the second part of https://stackoverflow.com/a/13293460/165603 (things work similarly except the extra M2M manager)
When being used inside User.objects.filter, both user_followees__follower=foo and user_followers__followee=foo would cause joining of the table of the Follower_to_followee model and a where condition checking for follower=foo or followee=foo
(Note that user_followees__followee=foo or user_followerers__follower=foo works differently from above, Django ORM simplifies them smartly and would generate something like User.objects.filter(pk=foo.pk)).

Answer 2

I'm not entirely sure I understand the question, but here is a simple solution. Note that this could be written more succinctly, but I broke it up so you can see each step.
How can I select all followees for a specific follower?
# First grab all the follower_to_followee entries for a given
# follower called: the_follower
follows = Follower_to_followee.objects.filter(follower=the_follower)
followee_counts = []
# Next, let's iterate through those objects and pick out
# the followees and their posts
for follow in follows:
followee = follow.followee
# post for each followee
followee_posts = Post.objects.filter(auth_user=followee).count()
# Count number of posts in the queryset
count = followee_posts.count()
# Add followee/post_counts to our list of followee_counts
followee_counts.append((followee, count))
# followee_counts is now a list of followee/post_count tuples

Answer 3

For get post counts you can use this:
#get follower
follower = User.objects.get(username='username_of_fallower')
#get all followees for a specific follower
for element in Follower_to_followee.objects.filter(follower=follower):
element.followee.post_set.all().count()

Answer 4

views.py
def view_name(request):
followers = Follower_to_followee.objects.filter(user=request.user)
.......
html
{{user}}<br/>
My followers:<br/>
{% follower in followers %}
<p>{{follower}} - {{follower.user.follower_to_followee_set.count}}</p>
{% endfor %}