def ensure_schema(self):
        # If the table's there, that's fine - we've never changed its schema
        # in the codebase.
        if self.Migration._meta.db_table in self.connection.introspection.table_names(self.connection.cursor()):
            return
        # Make the table
        try:
            with self.connection.schema_editor() as editor:
                editor.create_model(self.Migration)
        except DatabaseError as exc:
            raise MigrationSchemaMissing("Unable to create the django_migrations table (%s)" % exc)
Sets the number of instances for this server to run.
dataset/ETHPy150Open django/django/django/db/migrations/recorder.py/MigrationRecorder.ensure_schema--crossover with--dataset/ETHPy150Open AppScale/appscale/AppServer/google/appengine/tools/devappserver2/server.py/Server.set_num_instances