Question

How come it is not possible to save the entry when I fetch it by using filter?
It works if I fetch it with get.

I need to use filter since I’m using the serializer to return a JSON object. And Django’s serializer doesn’t like if it is not a QuerySet.

message = UserMessage.objects.filter(id=request.GET['msg_id'])
message[0].read = True
message[0].save()

Answer 1

Unless the message is evaluated and thus cached, the message[0] always hits DB, for example

>>> qs = User.objects.all()
>>> qs[0] is qs[0]
False
>>> bool(qs) # evaluate, len(qs) or iterating on qs also do
>>> qs[0] is qs[0]
True

you could assign it to variable

message = UserMessage.objects.filter(id=request.GET['msg_id'])[0]
message.read = True
message.save()

or use update directly, as jpic suggested:

UserMessage.objects.filter(id=request.GET['msg_id']).update(read=True)