empty queryset handling

django_querysets_single_query_fetch/service.py

@@ -51,6 +51,8 @@ def __init__(self, queryset: QuerySet) -> None:
 
 QuerysetWrapperType = Union[QuerySet, QuerysetCountWrapper, QuerysetGetOrNoneWrapper]
 
+RESULT_PLACEHOLDER = object()
+
 
 class QuerysetsSingleQueryFetch:
     """
@@ -379,6 +381,17 @@ def _convert_raw_results_to_final_queryset_results(
 
         return queryset_results
 
+    def _get_empty_queryset_value(self, queryset: QuerysetWrapperType) -> Any:
+        if isinstance(queryset, QuerysetCountWrapper):
+            empty_sql_val = 0
+        elif isinstance(queryset, QuerysetGetOrNoneWrapper):
+            empty_sql_val = None
+        else:
+            # normal queryset
+            empty_sql_val = []
+
+        return empty_sql_val
+
     def execute(self) -> list[list[Any]]:
         django_sqls_for_querysets = [
             self._get_django_sql_for_queryset(queryset=queryset)
@@ -387,12 +400,14 @@ def execute(self) -> list[list[Any]]:
 
         final_result_list: List[Any] = []
 
-        for queryset_sql in django_sqls_for_querysets:
+        for queryset_sql, queryset in zip(django_sqls_for_querysets, self.querysets):
             if not queryset_sql:
-                final_result_list.append([])
+                final_result_list.append(
+                    self._get_empty_queryset_value(queryset=queryset)
+                )
             else:
                 final_result_list.append(
-                    None
+                    RESULT_PLACEHOLDER
                 )  # will be replaced by actual result below
 
         non_empty_django_sqls_for_querysets = [
@@ -415,8 +430,8 @@ def execute(self) -> list[list[Any]]:
         final_result = []
         index = 0
         for queryset, result in zip(self.querysets, final_result_list):
-            if result is not None:
-                # empty case EmptyResultSet
+            if result is not RESULT_PLACEHOLDER:
+                # empty sql case
                 final_result.append(result)
                 continue
             final_result.append(

setup.py

@@ -2,7 +2,7 @@
 
 setuptools.setup(
     name="django_querysets_single_query_fetch",
-    version="0.0.9",
+    version="0.0.10",
     description="Execute multiple Django querysets in a single SQL query",
     long_description="Utility which executes multiple Django querysets over a single network/query call and returns results which would have been returned in normal evaluation of querysets",
     author="Nishant Singh",

testapp/tests/test_count_wrapper_for_postgres.py

@@ -24,13 +24,7 @@ def setUp(self) -> None:
             StoreProduct, store=self.store, category=self.category, selling_price=100.33
         )
 
-    def test_fetch_count(self):
-        """
-        - test fetch count works in single query
-        _ test fetch count works with filter querysets
-        _ test fetch count works with other querysets
-        """
-        # test fetch count works in single query
+    def test_works_in_simple_case(self):
         count_queryset = StoreProduct.objects.filter()
         with self.assertNumQueries(1):
             results = QuerysetsSingleQueryFetch(
@@ -41,7 +35,7 @@ def test_fetch_count(self):
         self.assertEqual(len(results), 1)
         self.assertEqual(results[0], count_queryset.count())
 
-        # test fetch count works with filter querysets
+    def test_works_with_filtered_queryset(self):
         count_filter_queryset = StoreProduct.objects.filter(id=self.product_1.id)
         with self.assertNumQueries(1):
             results = QuerysetsSingleQueryFetch(
@@ -52,7 +46,7 @@ def test_fetch_count(self):
         self.assertEqual(len(results), 1)
         self.assertEqual(results[0], count_filter_queryset.count())
 
-        # test fetch count works with other querysets
+    def test_works_with_other_querysets(self):
         count_queryset = StoreProduct.objects.filter()
         count_filter_queryset = StoreProduct.objects.filter(id=self.product_1.id)
         queryset = StoreProduct.objects.filter()
@@ -68,3 +62,13 @@ def test_fetch_count(self):
         self.assertEqual(results[0], count_queryset.count())
         self.assertEqual(results[1], count_filter_queryset.count())
         self.assertEqual(results[2], list(queryset))
+
+    def test_count_is_returned_as_zero_for_empty_queryset(self):
+        with self.assertNumQueries(0):
+            results = QuerysetsSingleQueryFetch(
+                querysets=[
+                    QuerysetCountWrapper(StoreProduct.objects.none()),
+                ]
+            ).execute()
+        self.assertEqual(len(results), 1)
+        self.assertEqual(results[0], 0)

testapp/tests/test_get_or_none_wrapper_for_postgres.py

@@ -60,3 +60,13 @@ def test_get_or_none_wrapper_with_multiple_rows_matching(self):
         self.assertTrue(
             (product.id == self.product_1.id) or (product.id == self.product_2.id)
         )
+
+    def test_get_or_none_wrapper_with_empty_queryset(self):
+        with self.assertNumQueries(0):
+            results = QuerysetsSingleQueryFetch(
+                querysets=[
+                    QuerysetGetOrNoneWrapper(StoreProduct.objects.none()),
+                ]
+            ).execute()
+        self.assertEqual(len(results), 1)
+        self.assertIsNone(results[0])