Django-与过滤器相关的计数

Question

I have a model called Article and I have a model called Comment which has a foreignkey to Article . I want to count from a Article queryset all comments in that queryset.

Example: I have a queryset with 5 articles and every article has 3 comments except for one. -> This should return 12.

Another example: One article has 3 comments and another one has 5 and other articles have no comments. -> This should return 8.

I tried it with:

Article.objects.all().annotate(comments_count=Count("comment", filter=Q(is_deleted=False))).comments_count

Answer 1

You should .aggregate(..) [Django-doc] here, not annotate(..) [Django-doc] . Annotating adds a value to each item in the original queryset. We can thus generate a query like:

Article.objects.(
    comments_count=Count('comment', filter=Q(comment__is_deleted=False))
)

Although it might be simpler to use the Comment model itself here, like:

.objects.filter(
    is_deleted=False,
    article__in=my_article_qs
)