CODEWITHSUNDEEP
djangodjango-queryset
Adam Starrh
Adam Starrh

Reputation: 6958

Django Querysets - Objects including entire set in ManyToMany

I have a model, Respondent, related to another model Questionnaire via a ManyToMany field named finished.

I have a set of four Questionnaire objects and would like to retrieve all Respondent objects that have a finished relationship with all four.

I would also like to retrieve the inverse: Any Respondent object which doesn't have a finished relationship with all four selected Questionnaire objects.

I've been looking through the docs, and haven't found something that works for me. I am able to get all of the Respondent objects that match at least one of the Questionnaire objects with Respondent.objects.filter(finished__in=questionnaire_queryset) but that's as far as I've gotten.

Upvotes: 2

Views: 29

Answers (1)

willeM_ Van Onsem
willeM_ Van Onsem

Reputation: 476659

You could count the number of finished objects that are in the questionnaire_queryset, like:

from django.db.models import Count

Respondent.objects.filter(
    finished__in=questionnaire_queryset
).annotate(
    nfinish=Count('finished')
).filter(
    nfinish=len(questionnaire_queryset)
)

We make an assumption here that questionnaire_queryset does not contain any duplicates.

Upvotes: 2

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