[Django]-Getting value of field of a reverse related model in django queryset

by

3👍

✅

I think I’ve found the answer.

qs = User.objects.annotate(
        last_message_time=Max("messages__created_at"),
        last_message_message=Subquery(
            Chat.objects.filter(user=OuterRef("id")).order_by("-created_at").values("message")[:1]
        )
     ).order_by("-last_message_time")

I got help from this article on this issue!
https://medium.com/@hansonkd/the-dramatic-benefits-of-django-subqueries-and-annotations-4195e0dafb16

👤Mehran

1👍

I don’t think you can do it easily with one query. This looks like exactly what you are looking for.

You can either write a custom raw SQL query to get what you want or do something not efficient like that in two steps:

qs = User.objects.annotate(
       last_message_time=Max("messages__created_at"),
    ).order_by("-last_message_time")

for user in qs:
    user.last_message = Chat.objects.get(user=user, created_at=user.last_message_time)
👤Cyrlop

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