django: implement DatabaseOperations.date_interval_sql()

fixes #184

Author: timgraham

spanner/django/features.py

@@ -61,9 +61,6 @@ class DatabaseFeatures(BaseDatabaseFeatures):
         # https://github.com/orijtech/spanner-orm/issues/155
         'timezones.tests.LegacyDatabaseTests.test_raw_sql',
         'timezones.tests.NewDatabaseTests.test_raw_sql',
-        # implement DatabaseOperations.date_interval_sql()
-        # https://github.com/orijtech/spanner-orm/issues/184
-        'timezones.tests.NewDatabaseTests.test_update_with_timedelta',
         # Unable to infer type for parameter:
         # https://github.com/orijtech/spanner-orm/issues/185
         'timezones.tests.LegacyDatabaseTests.test_cursor_execute_returns_naive_datetime',

spanner/django/operations.py

@@ -8,6 +8,7 @@
 from django.db.backends.base.operations import BaseDatabaseOperations
 from django.db.utils import DatabaseError
 from django.utils import timezone
+from django.utils.duration import duration_microseconds
 from spanner.dbapi.parse_utils import DateStr, TimestampStr, escape_name
 
 
@@ -174,6 +175,9 @@ def datetime_trunc_sql(self, lookup_type, field_name, tzname):
             sql = 'TIMESTAMP_ADD(' + sql + ', INTERVAL 1 DAY)'
         return sql
 
+    def date_interval_sql(self, timedelta):
+        return 'INTERVAL %s MICROSECOND' % duration_microseconds(timedelta)
+
     def format_for_duration_arithmetic(self, sql):
         return 'INTERVAL %s MICROSECOND' % sql