add DatabaseOperations.format_for_duration_arithmetic()

Author: timgraham

django_mongodb/features.py

@@ -255,8 +255,6 @@ def django_test_expected_failures(self):
             # Func not implemented.
             "annotations.tests.NonAggregateAnnotationTestCase.test_custom_functions",
             "annotations.tests.NonAggregateAnnotationTestCase.test_custom_functions_can_ref_other_functions",
-            # BaseDatabaseOperations may require a format_for_duration_arithmetic().
-            "annotations.tests.NonAggregateAnnotationTestCase.test_mixed_type_annotation_date_interval",
             # FieldDoesNotExist with ordering.
             "annotations.tests.AliasTests.test_order_by_alias",
             "annotations.tests.NonAggregateAnnotationTestCase.test_annotation_with_m2m",

django_mongodb/operations.py

@@ -218,5 +218,8 @@ def datetime_cast_date_sql(self, sql, params, tzname):
     def datetime_cast_time_sql(self, sql, params, tzname):
         return f"({sql})::time", params
 
+    def format_for_duration_arithmetic(self, sql):
+        return "INTERVAL %s MILLISECOND" % sql
+
     def time_trunc_sql(self, lookup_type, sql, params, tzname=None):
         return f"DATE_TRUNC(%s, {sql})::time", (lookup_type, *params)