def getall(self):
        try:
            spec = {'data': {'$exists': 1}}
            fields = {'_id': 0}
            sort = [('tid', 1)]
            cur = self.db.docs.find(spec, fields, sort=sort)
        except Exception as e:
            raise DatabaseException(e)
        return [Document(**row) for row in cur]
def queue_when_in_transaction(call):
    if transaction_states[call.using]:
        transaction_states[call.using].push((call, (), {}))
    else:
        return call()