django: fix BinaryField value set on existing rows

When setting values on existing rows, SchemaEditor.add_field() must pass
values as parameters for Spanner to handle them correctly.

fixes #388

Author: timgraham

packages/django-google-spanner/django_spanner/features.py

@@ -263,9 +263,6 @@ class DatabaseFeatures(BaseDatabaseFeatures):
         'schema.tests.SchemaTests.test_primary_key',
         # Spanner limitation:  Cannot remove a column from the primary key.
         'schema.tests.SchemaTests.test_alter_int_pk_to_int_unique',
-        # adding BinaryField sets wrong value on existing rows:
-        # https://github.com/orijtech/django-spanner/issues/388
-        'migrations.test_operations.OperationTests.test_add_binaryfield',
         # changing a not null constraint isn't allowed if it affects an index:
         # https://github.com/orijtech/django-spanner/issues/378
         'migrations.test_operations.OperationTests.test_alter_field_with_index',

packages/django-google-spanner/django_spanner/schema.py

@@ -128,11 +128,10 @@ def add_field(self, model, field):
         # defaults for this but Spanner doesn't support them.)
         effective_default = self.effective_default(field)
         if effective_default is not None:
-            self.execute('UPDATE %(table)s SET %(column)s=%(value)r' % {
+            self.execute('UPDATE %(table)s SET %(column)s=%%s' % {
                 "table": self.quote_name(model._meta.db_table),
                 "column": self.quote_name(field.column),
-                "value": effective_default,
-            })
+            }, (effective_default,))
         # Spanner doesn't support adding NOT NULL columns to existing tables.
         if not field.null:
             self.execute(self.sql_alter_column % {