Features: 1) Optimize retrieval of filterable attributes by grouping attribute values and reducing query overhead;

Fixes: 1) Handle `user` lookup more robustly using `getattr`; 2) Prevent redundant list creation in distinct value processing;

Extra: 1) Use consistent cache key variable; 2) Improve code readability with `defaultdict` for grouping; 3) Minor cleanup and formatting enhancements; 4) Remove unnecessary attribute redefinitions.

core/serializers/detail.py

@@ -75,42 +75,46 @@ class CategoryDetailSerializer(ModelSerializer):
         return None
 
     def get_filterable_attributes(self, obj: Category) -> list[dict]:
-        filterable_results = cache.get(f"{obj.uuid}_filterable_results", [])
-
+        cache_key = f"{obj.uuid}_filterable_results"
+        filterable_results = cache.get(cache_key)
         if filterable_results:
             return filterable_results
 
-        request: Request | None = self.context.get("request")
-        user: User | AnonymousUser | None = getattr(request, "user")  # noqa: B009
+        request = self.context.get("request")
+        user = getattr(request, "user", AnonymousUser())
+        attrs_qs = obj.attributes.all() if user.has_perm("view_attribute") else obj.attributes.filter(is_active=True)
+        attributes = list(attrs_qs)
 
-        if user is None:
-            user = AnonymousUser()
-
-        attributes = obj.attributes.all() if user.has_perm("view_attribute") else obj.attributes.filter(is_active=True)
-
-        for attr in attributes:
-            distinct_vals = (
+        attr_ids = [a.id for a in attributes]
+        raw_vals = (
             AttributeValue.objects.annotate(value_length=Length("value"))
-                .filter(attribute=attr, product__category=obj, value_length__lte=30)
-                .values_list("value", flat=True)
+            .filter(
+                attribute_id__in=attr_ids,
+                product__category=obj,
+                value_length__lte=30,
+            )
+            .values_list("attribute_id", "value")
             .distinct()
         )
 
-            distinct_vals_list = list(distinct_vals)[0:128] if len(list(distinct_vals)) > 128 else list(distinct_vals)
+        grouped = defaultdict(list)
+        for attr_id, val in raw_vals:
+            grouped[attr_id].append(val)
 
+        filterable_results = []
+        for attr in attributes:
+            vals = grouped.get(attr.id, [])
+            slice_vals = vals[:128] if len(vals) > 128 else vals
             filterable_results.append(
                 {
                     "attribute_name": attr.name,
-                    "possible_values": distinct_vals_list,
+                    "possible_values": slice_vals,
                     "value_type": attr.value_type,
                 }
             )
 
-        if user is None:
-            user = AnonymousUser()
-
         if not user.has_perm("view_attribute"):
-            cache.set(f"{obj.uuid}_filterable_results", filterable_results, 86400)
+            cache.set(cache_key, filterable_results, 86400)
 
         return filterable_results