.only().prefetch_related() 给出 'ManyToOneRel' 对象没有属性 'attname'

Question

i am fetching required fields of a table after a select_related() and prefetch_related() on the same query using .only()

I can't seem to get the result from prefetch_related probably because .only() is restricting access to its result ?

I have tried adding prefetch_related field in .only() as well but to no avail.

Feedback.objects.all().select_related(
            'feedback_option'
        ).only(
            'feedback_option',

            # tried with and without either one or both of the following
            'feedback__remarks',
            'feedback__remarks__text'
        ).prefetch_related(
            Prefetch(
                'feedback__remarks',
                queryset=FeedbackRemark.objects.all().only('text'),
            ),
        )

I am getting the following exception because of this.

AttributeError: 'ManyToOneRel' object has no attribute 'attname'

I am using django 1.10.5

Answer 1

Have the same problem, solved it by replacing .only() with .defer(), listing all unused fields. This shorten the memory used, at no additional db queries.