def database_forwards(self, app_label, schema_editor, from_state, to_state):
        """Perform forward migration."""
        from resolwe.flow.models.data import DataQuerySet
        # pylint: disable=protected-access

        Data = from_state.apps.get_model('flow', 'Data')  # pylint: disable=invalid-name
        DataQuerySet._delete_chunked(Data.objects.filter(process__slug=self.process))

        Process = from_state.apps.get_model('flow', 'Process')  # pylint: disable=invalid-name
        Process.objects.filter(slug=self.process).delete()