Part API query tests (#4423)

* Add unit tests for validating number of queries

* Simplify category_detail annotation to PartList API endpoint

- Previous approach was an old hack from before the n+1 problem was understood

InvenTree/part/api.py

@@ -1118,6 +1118,7 @@ class PartList(APIDownloadMixin, ListCreateAPI):
             params = self.request.query_params
 
             kwargs['parameters'] = str2bool(params.get('parameters', None))
+            kwargs['category_detail'] = str2bool(params.get('category_detail', False))
 
         except AttributeError:
             pass
@@ -1156,41 +1157,6 @@ class PartList(APIDownloadMixin, ListCreateAPI):
 
         data = serializer.data
 
-        # Do we wish to include PartCategory detail?
-        if str2bool(request.query_params.get('category_detail', False)):
-
-            # Work out which part categories we need to query
-            category_ids = set()
-
-            for part in data:
-                cat_id = part['category']
-
-                if cat_id is not None:
-                    category_ids.add(cat_id)
-
-            # Fetch only the required PartCategory objects from the database
-            categories = PartCategory.objects.filter(pk__in=category_ids).prefetch_related(
-                'parts',
-                'parent',
-                'children',
-            )
-
-            category_map = {}
-
-            # Serialize each PartCategory object
-            for category in categories:
-                category_map[category.pk] = part_serializers.CategorySerializer(category).data
-
-            for part in data:
-                cat_id = part['category']
-
-                if cat_id is not None and cat_id in category_map.keys():
-                    detail = category_map[cat_id]
-                else:
-                    detail = None
-
-                part['category_detail'] = detail
-
         """
         Determine the response type based on the request.
         a) For HTTP requests (e.g. via the browseable API) return a DRF response

InvenTree/part/serializers.py

@@ -470,22 +470,19 @@ class PartSerializer(RemoteImageMixin, InvenTreeModelSerializer):
         - Allows us to optionally pass extra fields based on the query.
         """
         self.starred_parts = kwargs.pop('starred_parts', [])
-
         category_detail = kwargs.pop('category_detail', False)
-
         parameters = kwargs.pop('parameters', False)
-
         create = kwargs.pop('create', False)
 
         super().__init__(*args, **kwargs)
 
-        if category_detail is not True:
+        if not category_detail:
             self.fields.pop('category_detail')
 
-        if parameters is not True:
+        if not parameters:
             self.fields.pop('parameters')
 
-        if create is not True:
+        if not create:
             # These fields are only used for the LIST API endpoint
             for f in self.skip_create_fields()[1:]:
                 self.fields.pop(f)

InvenTree/part/test_api.py

@@ -5,6 +5,8 @@ from enum import IntEnum
 from random import randint
 
 from django.core.exceptions import ValidationError
+from django.db import connection
+from django.test.utils import CaptureQueriesContext
 from django.urls import reverse
 
 import PIL
@@ -1704,6 +1706,60 @@ class PartDetailTests(PartAPITestBase):
         self.assertEqual(part.metadata['x'], 'y')
 
 
+class PartListTests(PartAPITestBase):
+    """Unit tests for the Part List API endpoint"""
+
+    def test_query_count(self):
+        """Test that the query count is unchanged, independent of query results"""
+
+        queries = [
+            {'limit': 1},
+            {'limit': 10},
+            {'limit': 50},
+            {'category': 1},
+            {},
+        ]
+
+        url = reverse('api-part-list')
+
+        # Create a bunch of extra parts (efficiently)
+        parts = []
+
+        for ii in range(100):
+            parts.append(Part(
+                name=f"Extra part {ii}",
+                description="A new part which will appear via the API",
+                level=0, tree_id=0,
+                lft=0, rght=0,
+            ))
+
+        Part.objects.bulk_create(parts)
+
+        for query in queries:
+
+            with CaptureQueriesContext(connection) as ctx:
+                self.get(url, query, expected_code=200)
+
+            # No more than 20 database queries
+            self.assertLess(len(ctx), 20)
+
+        # Test 'category_detail' annotation
+        for b in [False, True]:
+            with CaptureQueriesContext(connection) as ctx:
+                results = self.get(
+                    reverse('api-part-list'),
+                    {'category_detail': b},
+                    expected_code=200
+                )
+
+                for result in results.data:
+                    if b and result['category'] is not None:
+                        self.assertIn('category_detail', result)
+
+            # No more than 20 DB queries
+            self.assertLessEqual(len(ctx), 20)
+
+
 class PartNotesTests(InvenTreeAPITestCase):
     """Tests for the 'notes' field (markdown field)"""