public function getParentId()
    {
        // when this field will be introduced there will be no need to load from real article
        if (isset($this->oxorderarticles__oxartparentid) && $this->oxorderarticles__oxartparentid->value !== false) {
            return $this->oxorderarticles__oxartparentid->value;
        }

        $oDb = \OxidEsales\Eshop\Core\DatabaseProvider::getDb();
        $oArticle = oxNew(\OxidEsales\Eshop\Application\Model\Article::class);
        $sQ = "select oxparentid from " . $oArticle->getViewName() . " where oxid=" . $oDb->quote($this->getProductId());
        $this->oxarticles__oxparentid = new \OxidEsales\Eshop\Core\Field($oDb->getOne($sQ));

        return $this->oxarticles__oxparentid->value;
    }