protected function getTagsFromMySQL()
    {
        $queryParts = $this->getQueryParts();

        $queryBuilder = self::getQueryBuilder('tx_kesearch_index');
        $queryBuilder->getRestrictions()->removeAll();

        $tagRows = $queryBuilder
            ->select('tags')
            ->from($queryParts['FROM'])
            ->add('where', $queryParts['WHERE'])
            ->execute()
            ->fetchAll();

        return array_map(
            function ($row) {
                return $row['tags'];
            },
            $tagRows
        );
    }