Django filter with two constraints on related model

Question

I have a django app with models as follows:

• A Question model

• An Answer model, with a ForeignKey back to the Question. (A question can have multiple answers.)

• A Flag model, with a ForeignKey to the Answer. (An answer can be flagged as inappropriate.)

All of the above also have a user field, defining the user that created that object.

I'm trying to get a list of all Questions with answers from the current user which have been flagged. I tried this:

Question.objects.filter(answer__user=user).\
                 filter(answer__flag__isnull=False).distinct()

… but I believe that will return a list of Questions with answers from the current user and with answers which have been flagged, but will not necessarily guarantee that it is the user's answer that has been flagged.

Is there an easy way to do this? Basically, I want to make the answer part of the filter refer to the same answer on both of them.

Please let me know if something is unclear.

Answer 1

How about:

questions = [a.question for a in user.answer_set.filter(flag__isnull=True)]

Edit: this does not return a queryset, of course. And to prevent duplicate questions, maybe wrap the list comprehension in a set().

Answer 2

The query does exactly what you want, except that you should filter for questions where the flag is not null. Chained filters are anded together, so it will filter out all questions that have an answer from the particular user and then filter that set for answers that are flagged.

You may also put those two criteria in the same filter call:

Question.objects.filter(answer__user=user, answer__flag__isnull=False)