Question

class Post(models.Model):
    title = ...
    category = models.ForeignKey(Category)
    date = .......

class Category(models.Model):
    title = ....

On the main page i want to display 5 posts with latest dates, but all posts must be from different categories. There is 50 categoriese, for example. Is it possible?

Answer 1

from django.db.models import Max

categories = Category.objects.annotate(most_recent=Max(post__date)).order_by('-most_recent')[:5]

posts = list()
for category in categories:
  posts.append(category.post_set.latest())

That annotates the categories with the date of the most recent post as the value of most_recent, which you can then order by to get the 5 most recent categories.

Then, just loop through the categories and pull out the latest post for each. Done.