Improve StockItem API speed (#5042)

- Removes child detail fields which cannot be effectively annotated
- Prefetch required fields
- Add unit test method for checking query count

InvenTree/stock/api.py

@@ -795,15 +795,6 @@ class StockList(APIDownloadMixin, ListCreateDestroyAPIView):
 
         queryset = StockSerializers.StockItemSerializer.annotate_queryset(queryset)
 
-        # Also ensure that we pre-fecth all the related items
-        queryset = queryset.prefetch_related(
-            'part',
-            'part__category',
-            'location',
-            'test_results',
-            'tags',
-        )
-
         return queryset
 
     def filter_queryset(self, queryset):

InvenTree/stock/serializers.py

@@ -231,10 +231,17 @@ class StockItemSerializer(InvenTree.serializers.InvenTreeTagModelSerializer):
         """Add some extra annotations to the queryset, performing database queries as efficiently as possible."""
 
         queryset = queryset.prefetch_related(
+            'location',
             'sales_order',
             'purchase_order',
             'part',
+            'part__category',
             'part__pricing_data',
+            'supplier_part',
+            'supplier_part__manufacturer_part',
+            'supplier_part__tags',
+            'test_results',
+            'tags',
         )
 
         # Annotate the queryset with the total allocated to sales orders
@@ -280,7 +287,7 @@ class StockItemSerializer(InvenTree.serializers.InvenTreeTagModelSerializer):
     status_text = serializers.CharField(source='get_status_display', read_only=True)
 
     # Optional detail fields, which can be appended via query parameters
-    supplier_part_detail = SupplierPartSerializer(source='supplier_part', many=False, read_only=True)
+    supplier_part_detail = SupplierPartSerializer(source='supplier_part', supplier_detail=False, manufacturer_detail=False, part_detail=False, many=False, read_only=True)
     part_detail = PartBriefSerializer(source='part', many=False, read_only=True)
     location_detail = LocationBriefSerializer(source='location', many=False, read_only=True)
     tests = StockItemTestResultSerializer(source='test_results', many=True, read_only=True)

InvenTree/stock/test_api.py

@@ -557,6 +557,42 @@ class StockItemListTest(StockAPITestCase):
 
         self.assertEqual(len(dataset), 17)
 
+    def test_query_count(self):
+        """Test that the number of queries required to fetch stock items is reasonable."""
+
+        def get_stock(data):
+            """Helper function to fetch stock items."""
+            response = self.client.get(self.list_url, data=data)
+            self.assertEqual(response.status_code, 200)
+            return response.data
+
+        # Create a bunch of StockItem objects
+        prt = Part.objects.first()
+
+        StockItem.objects.bulk_create([
+            StockItem(
+                part=prt,
+                quantity=1,
+                level=0, tree_id=0, lft=0, rght=0,
+            ) for _ in range(100)
+        ])
+
+        # List *all* stock items
+        with self.assertNumQueriesLessThan(25):
+            get_stock({})
+
+        # List all stock items, with part detail
+        with self.assertNumQueriesLessThan(20):
+            get_stock({'part_detail': True})
+
+        # List all stock items, with supplier_part detail
+        with self.assertNumQueriesLessThan(20):
+            get_stock({'supplier_part_detail': True})
+
+        # List all stock items, with 'location' and 'tests' detail
+        with self.assertNumQueriesLessThan(20):
+            get_stock({'location_detail': True, 'tests': True})
+
 
 class StockItemTest(StockAPITestCase):
     """Series of API tests for the StockItem API."""