public function load(QueryBuilder $query, ClassMetadata $metadata)
    {
        $field = $this->mapping['fieldname'];
        $boltname = $metadata->getBoltName();
        $table = $this->mapping['tables']['field_value'];

        $from = $query->getQueryPart('from');

        if (isset($from[0]['alias'])) {
            $alias = $from[0]['alias'];
        } else {
            $alias = $from[0]['table'];
        }

        $subQuery = '(SELECT ' . $this->getPlatformGroupConcat($query) . " FROM $table f WHERE f.content_id = $alias.id AND f.contenttype='$boltname' AND f.name = '$field') as $field";
        $query->addSelect($subQuery);

        return null;
    }