fix HomeView N+1 and cache the curriculum tree

GET /api/home is the most-hit authenticated endpoint (every app open) and was running one COUNT per node. Now it is a flat number of queries regardless of grade size, and the shared curriculum skeleton is served from cache; per-user progress/stats stay live. content/views.py - _node_status(): takes a precomputed set of completed lesson_ids and a node's lesson_ids instead of firing its own COUNT query. - HomeView.get(): one query for all completed lesson_ids of the user in the grade, status computed in Python; grade tree (units -> nodes -> lesson_ids, no per-user data) read from cache (content:tree:grade:{id}:v{N}); missing grade -> 404 (was an unhandled 500); grade with no units -> empty units, not 404. - GradesListView: served from cache (content:grades:v{N}). - curriculum_version() / bump_curriculum_version(): one shared version key; bumping it invalidates every content cache key at once. - both GET views get throttle_scope='read' + GuestAwareContentThrottle. content/receivers.py - post_save/post_delete on Grade/Unit/Node/Lesson -> bump_curriculum_version(). content/tests.py - HomeViewScalabilityTests: query count flat for 2 vs 20 nodes; 2nd call hits cache (no content_unit/node SQL); a new Node invalidates the tree; missing grade 404; empty grade 200. - GradesListCacheTests: list cached, invalidated on new Grade. - ReadThrottleTests: /api/home returns 429 past the limit. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
2026-08-30 08:45:18 +03:30
parent eeb6bd6138
commit 35218bf6a1
3 changed files with 231 additions and 21 deletions
--- a/content/views.py
+++ b/content/views.py
@@ -1,4 +1,6 @@
+from django.core.cache import cache
 from django.db import IntegrityError, transaction
+from django.http import Http404
 from django.shortcuts import get_object_or_404
 from drf_spectacular.types import OpenApiTypes
 from drf_spectacular.utils import OpenApiParameter, extend_schema
@@ -45,28 +47,91 @@ class GuestAwareContentThrottle(ScopedRateThrottle):
        return self.cache_format % {'scope': self.scope, 'ident': ident}


+# --- کشِ داده‌ی شبهِ‌ثابتِ برنامه‌ی درسی -------------------------------------
+# گریدها و درختِ unit/node/lesson تقریباً هیچ‌وقت عوض نمی‌شوند ولی روی هر بار
+# باز شدنِ اپ خوانده می‌شوند. یک نسخه‌کلیدِ مشترک نگه می‌داریم که با هر تغییرِ
+# محتوا (سیگنال در content/receivers.py) یک واحد جلو می‌رود و همه‌ی کلیدهای
+# کشِ محتوا را یک‌جا باطل می‌کند. دیتای per-user (پیشرفت/آمار) کش نمی‌شود.
+_CURRICULUM_VERSION_KEY = 'content:curriculum:ver'
+_CACHE_TTL = 3600
+
+
+def curriculum_version() -> int:
+    return cache.get_or_set(_CURRICULUM_VERSION_KEY, 1, None) or 1
+
+
+def bump_curriculum_version() -> None:
+    try:
+        cache.incr(_CURRICULUM_VERSION_KEY)
+    except ValueError:
+        cache.set(_CURRICULUM_VERSION_KEY, curriculum_version() + 1, None)
+
+
+def _grades_payload() -> dict:
+    key = f'content:grades:v{curriculum_version()}'
+
+    def build():
+        return {'grades': [
+            {'id': g.id, 'title': g.title, 'icon': g.icon, 'color': g.color}
+            for g in Grade.objects.all().order_by('id')
+        ]}
+
+    return cache.get_or_set(key, build, _CACHE_TTL)
+
+
+def _grade_tree(grade_id: int):
+    """اسکلتِ گریدِ [{id,title,nodes:[{id,title,lesson_ids}]}] — بدونِ status/دیتای کاربر.
+    None یعنی گریدِ ناموجود؛ [] یعنی گریدِ موجودِ بدونِ واحد."""
+    key = f'content:tree:grade:{grade_id}:v{curriculum_version()}'
+    cached = cache.get(key)
+    if cached is not None:
+        return None if cached is False else cached
+
+    if not Grade.objects.filter(pk=grade_id).exists():
+        cache.set(key, False, _CACHE_TTL)
+        return None
+
+    units = (
+        Grade.objects.get(pk=grade_id)
+        .units.prefetch_related('nodes__lessons').all()
+    )
+    tree = [
+        {
+            'id': str(unit.id),
+            'title': unit.title,
+            'nodes': [
+                {
+                    'id': str(node.id),
+                    'title': node.title,
+                    'lesson_ids': [lsn.id for lsn in node.lessons.all()],
+                }
+                for node in unit.nodes.all()
+            ],
+        }
+        for unit in units
+    ]
+    cache.set(key, tree, _CACHE_TTL)
+    return tree
+
+
 class GradesListView(APIView):
    """GET /api/grades — لیست پایه‌ها"""

+    throttle_scope = 'read'
+    throttle_classes = [GuestAwareContentThrottle]
+
    @extend_schema(responses=GradesListResponseSerializer, tags=['Curriculum (content)'])
    def get(self, request):
-        grades = Grade.objects.all().order_by('id')
-        data = {'grades': [
-            {'id': g.id, 'title': g.title, 'icon': g.icon, 'color': g.color} for g in grades
-        ]}
-        return Response(GradesListResponseSerializer(data).data)
+        return Response(GradesListResponseSerializer(_grades_payload()).data)


-def _node_status(node, user_id, is_first_unlocked_candidate):
-    lesson_ids = list(node.lessons.values_list('id', flat=True))
+def _node_status(lesson_ids, completed_ids, is_first_unlocked_candidate):
    if not lesson_ids:
        return 'locked'
-    completed_count = UserLessonCompletion.objects.filter(
-        user_id=user_id, lesson_id__in=lesson_ids
-    ).values('lesson_id').distinct().count()
-    if completed_count >= len(lesson_ids):
+    done = sum(1 for lid in lesson_ids if lid in completed_ids)
+    if done >= len(lesson_ids):
        return 'completed'
-    if completed_count > 0 or is_first_unlocked_candidate:
+    if done > 0 or is_first_unlocked_candidate:
        return 'unlocked'
    return 'locked'

@@ -76,6 +141,8 @@ class HomeView(APIView):

    # userId همیشه از request.user.id (توکن معتبر) گرفته می‌شود، نه ورودی کلاینت (IDOR).
    permission_classes = [IsAuthenticated]
+    throttle_scope = 'read'
+    throttle_classes = [GuestAwareContentThrottle]

    @extend_schema(
        parameters=[
@@ -88,19 +155,36 @@ class HomeView(APIView):
        grade_id = request.query_params.get('grade')
        user_id = request.user.id

-        units_qs = Grade.objects.get(pk=grade_id).units.all() if grade_id else []
+        tree = []
+        if grade_id:
+            try:
+                tree = _grade_tree(int(grade_id))
+            except (TypeError, ValueError):
+                raise Http404
+            if tree is None:
+                raise Http404
+
+        # همه‌ی lesson_idهای کامل‌شده‌ی این کاربر در همین گرید — یک کوئری،
+        # مستقل از تعدادِ node (رفعِ N+1).
+        all_lesson_ids = [lid for unit in tree for node in unit['nodes'] for lid in node['lesson_ids']]
+        completed_ids = set()
+        if all_lesson_ids:
+            completed_ids = set(
+                UserLessonCompletion.objects.filter(
+                    user_id=user_id, lesson_id__in=all_lesson_ids
+                ).values_list('lesson_id', flat=True)
+            )

        units_payload = []
-        for unit in units_qs:
-            nodes = list(unit.nodes.all())
+        for unit in tree:
            node_payload = []
            unlock_next = True  # اولین نودِ قفل‌نشده در هر واحد، باز می‌مونه
-            for node in nodes:
-                node_status = _node_status(node, user_id, unlock_next)
+            for node in unit['nodes']:
+                node_status = _node_status(node['lesson_ids'], completed_ids, unlock_next)
                if node_status != 'completed':
                    unlock_next = False
-                node_payload.append({'id': str(node.id), 'title': node.title, 'status': node_status})
-            units_payload.append({'id': str(unit.id), 'title': unit.title, 'nodes': node_payload})
+                node_payload.append({'id': node['id'], 'title': node['title'], 'status': node_status})
+            units_payload.append({'id': unit['id'], 'title': unit['title'], 'nodes': node_payload})

        stats = UserStats.objects.filter(user_id=user_id).first()
        stats_payload = {