Re-structure some querying on cart and order pages to reduce load

src/pretix/presale/views/questions.py

@@ -1,7 +1,5 @@
-from django.db.models import Prefetch
 from django.utils.functional import cached_property
 
-from pretix.base.models import Question, QuestionAnswer, QuestionOption
 from pretix.base.views.mixins import BaseQuestionsViewMixin
 from pretix.presale.forms.checkout import QuestionsForm
 from pretix.presale.views import get_cart
@@ -13,27 +11,5 @@ class QuestionsViewMixin(BaseQuestionsViewMixin):
 
     @cached_property
     def _positions_for_questions(self):
-        qqs = self.request.event.questions.all()
-        if self.only_user_visible:
-            qqs = qqs.filter(ask_during_checkin=False, hidden=False)
-        cart = get_cart(self.request).select_related(
-            'addon_to'
-        ).prefetch_related(
-            'addons', 'addons__item', 'addons__variation',
-            Prefetch('answers',
-                     QuestionAnswer.objects.prefetch_related('options'),
-                     to_attr='answerlist'),
-            Prefetch('item__questions',
-                     qqs.prefetch_related(
-                         Prefetch('options', QuestionOption.objects.prefetch_related(Prefetch(
-                             # This prefetch statement is utter bullshit, but it actually prevents Django from doing
-                             # a lot of queries since ModelChoiceIterator stops trying to be clever once we have
-                             # a prefetch lookup on this query...
-                             'question',
-                             Question.objects.none(),
-                             to_attr='dummy'
-                         )))
-                     ).select_related('dependency_question'),
-                     to_attr='questions_to_ask')
-        )
+        cart = get_cart(self.request)
         return sorted(list(cart), key=self._keyfunc)