Django得到每个帖子的总和

问题描述

我有两个模型，Post和Vote。用户可以upvote和downvote帖子。

models.py：

  c $ c> > 
I have two models, Post and Vote. Users can upvote and downvote posts.

models.py:
class Post(models.Model):
    poster = models.ForeignKey('auth.User')
    question = models.ForeignKey('self', null=True, blank=True)
    post_title = models.CharField(max_length=300)
    post_content = models.TextField(null=True, blank=True)

    is_published = models.BooleanField(default=True)
    is_locked = models.BooleanField(default=False)
    is_question = models.BooleanField(default=True)
    is_deleted = models.BooleanField(default=False)

    created_date = models.DateTimeField(
            default=timezone.now)
    published_date = models.DateTimeField(
            blank=True, null=True)
    date_modified = models.DateTimeField(
            blank=True, null=True)

    def publish(self):
        self.published_date = timezone.now()
        self.save()

    def __str__(self):
        return self.post_title

class Vote(models.Model):
    user = models.ForeignKey('auth.User')
    post = models.ForeignKey('Post')
    vote_type = models.SmallIntegerField()#-1, 0, 1
    date_voted = models.DateTimeField(
            default=timezone.now)
    def __str__(self):
        return self.user
I use the following code in my view to return the posts to templates:
views.py:
def index(request):
    posts = Post.objects.filter(created_date__lte=timezone.now(
    ), is_question=1, is_published=1).order_by('-created_date')
    #removed the paging stuff here for simplification
    return render(request, 'homepage/index.html', {'posts': posts})
This just returns the posts, but I also want the sum of the vote_type column for each post which is the total number of votes for the post.
Currently I use template tags for each post to check for each post's votes.
My index.html sample code:
    {% for post in posts %}
       {{ post|total_votes|default:"0" }}
    {% endfor %}
Is there any way to query everything in the views.py and then in the template I could check like this: {{post.total_votes}}?
 解决方案 
Yeah, you can use annnotate. Generally, it would look something like
from django.db.models import Sum
posts = Post.objects.filter(...).annotate(total_votes=Sum('vote__vote_type'))
each post object in posts will then have a total_votes attribute.
                        
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