From 3e1cb4b54fdd90c463049d84bd58582108e52fd0 Mon Sep 17 00:00:00 2001
From: Ross <xkjq@ymail.com>
Date: Mon, 29 Dec 2025 12:09:18 +0000
Subject: [PATCH] Optimize question loading and user answer retrieval in
 ExamViews to reduce database queries

---
 generic/views.py | 29 +++++++++++++++--------------
 1 file changed, 15 insertions(+), 14 deletions(-)

diff --git a/generic/views.py b/generic/views.py
index 2366128f..7ac114d6 100644
--- a/generic/views.py
+++ b/generic/views.py
@@ -3436,29 +3436,30 @@ class ExamViews(View, LoginRequiredMixin):
         if user is None:
             user = request.user
 
-        questions = (
-            exam.get_questions()
-        )  # .prefetch_related("cid_user_answers", "answers")
+        # Load questions; prefetch 'answers' for apps that use them to avoid repeated DB hits
+        questions_qs = exam.get_questions()
+        if self.app_name not in ("physics",):
+            questions_qs = questions_qs.prefetch_related("answers")
 
-        # cid_user_answers = list(UserAnswer.objects.filter(cid=cid, exam__id=pk).prefetch_related("question"))
+        # Materialize questions list for iteration
+        questions = list(questions_qs)
 
-        # cid_user_answers_q_map = {}
+        # Fetch all relevant UserAnswer objects up-front to avoid per-question queries
+        if cid is not None:
+            user_answers_qs = self.UserAnswer.objects.filter(cid=cid, exam__id=pk).select_related("question")
+        else:
+            user_answers_qs = self.UserAnswer.objects.filter(user=user, exam__id=pk).select_related("question")
 
-        # for ans in cid_user_answers:
-        #    cid_user_answers_q_map[ans.question] = ans
+        # Map question_id -> UserAnswer for O(1) lookup
+        user_answers_map = {ua.question_id: ua for ua in user_answers_qs}
 
         answers_and_marks = []
         answers_marks = []
         answers = []
 
         for q in questions:
-            # Get user answer
-            if cid is not None:
-                user_answer = q.cid_user_answers.filter(cid=cid, exam__id=pk).first()
-            else:
-                user_answer = q.cid_user_answers.filter(
-                    user=request.user, exam__id=pk
-                ).first()
+            # Get user answer from the in-memory map (avoids N+1 queries)
+            user_answer = user_answers_map.get(q.pk)
             # user_answer = cid_user_answers_q_map[q]
 
             feedback = None