protected function getCachePersistence()
    {
        if (is_null($this->cachePersistence) && $this->hasOption(static::OPTION_CACHE_PERSISTENCE)) {
            $persistenceOption = $this->getOption(static::OPTION_CACHE_PERSISTENCE);
            $this->cachePersistence = (is_object($persistenceOption))
                ? $persistenceOption
                : common_persistence_KeyValuePersistence::getPersistence($persistenceOption);
        }

        return $this->cachePersistence;
    }