Django Querying Question

Question

If I were to have two different QuerySets in Django, both representing a ManyToMany relation with the same model, how would I find the intersections?

Answer 1

Merge your querysets in a list and next, create a set, you'll convert back to a list :

from itertools import chain
merged_qs = chain(queryset1, queryset2) 
intersection_list = list(set(list( merged_qs )))

Answer 2

1. order querysets by same set of keys
2. call iterator() on both querysets
3. feed iterators to intersect function from this answer: http://stackoverflow.com/questions/969709/joining-a-set-of-ordered-integer-yielding-python-iterators

Answer 3

You might be able to avoid the question by using the IN operator to create a subquery: http://docs.djangoproject.com/en/dev/ref/models/querysets/#in