Fix for N+1 issues in stock item serializing (#12534)

src/backend/InvenTree/stock/api.py

@@ -143,8 +143,16 @@ class StockItemSerialize(StockItemContextMixin, CreateAPI):
 
         queryset = StockSerializers.StockItemSerializer.annotate_queryset(items)
 
+        # Apply any additional prefetching required by optional fields which end up
+        # included in this response (e.g. 'tags', 'tests') - mirrors what
+        # OutputOptionsMixin.get_queryset() does for a normal list/retrieve request,
+        # which this manually-constructed response bypasses
+        context = self.get_serializer_context()
+        probe_serializer = StockSerializers.StockItemSerializer(context=context)
+        queryset = probe_serializer.prefetch_queryset(queryset)
+
         response = StockSerializers.StockItemSerializer(
-            queryset, many=True, context=self.get_serializer_context()
+            queryset, many=True, context=context
         )
 
         return Response(response.data, status=status.HTTP_201_CREATED)

src/backend/InvenTree/stock/models.py

@@ -2489,7 +2489,18 @@ class StockItem(
         # Create a new tracking entry for each item
         history_items = []
 
+        # Every new item shares this exact part - avoid a redundant per-item
+        # part_id -> Part lookup (bulk_create_and_fetch() does not preserve the
+        # cached FK) by seeding each item's cache with the instance we already have
+        part = self.part
+
+        # Check (once) whether there are any test results to copy across, rather
+        # than re-querying an identical (and usually empty) result set per item
+        has_test_results = self.test_results.exists()
+
         for item in items:
+            item.part = part
+
             # Construct tracking entries for the new StockItem
             if entry := item.add_tracking_entry(
                 StockHistoryCode.SPLIT_FROM_PARENT,
@@ -2512,6 +2523,7 @@ class StockItem(
                 history_items.append(entry)
 
             # Copy any test results from this item to the new one
+            if has_test_results:
                 item.copyTestResultsFrom(self)
 
         StockItemTracking.objects.bulk_create(history_items, batch_size=250)

src/backend/InvenTree/stock/test_api.py

@@ -1702,9 +1702,8 @@ class StockItemTest(StockAPITestCase):
         with self.settings(
             PLUGIN_TESTING_EVENTS=True, PLUGIN_TESTING_EVENTS_ASYNC=True
         ):
-            # TODO: 2026-07-12 : Refactor this API call
             response = self.post(
-                url, data, max_query_count=1300, benchmark=True, format='json'
+                url, data, max_query_count=150, benchmark=True, format='json'
             )
 
         self.assertEqual(response.status_code, 201)