Django: Select 3 most recent Post objects from 3 different users in a single database query

django_union_snippet.rst

Task

Given:

• There are a lot of Post objects.
• There are 3 users.

What we want:

• Select 3 most recent Post objects from 3 different users.

Models

class Post(models.Model):

    title = models.TextField()
    user = models.ForeignKey(settings.AUTH_USER_MODEL)
    date = models.DateTimeField()

Implementation

qs_1 = Post.objects.filter(user_id=1).order_by('-date')

qs_1.query.set_limits(0, 1)

qs_2 = Post.objects.filter(user_id=2).order_by('-date')

qs_2.query.set_limits(0, 1)

qs_3 = Post.objects.filter(user_id=3).order_by('-date')

qs_3.query.set_limits(0, 1)

qs = Post.objects.none()

qsa = qs.union(qs_1, qs_2, qs_3)

print(qsa)