protected function fetchUserId($fieldId)
    {
        $query = $this->connection->createQueryBuilder();
        $query
            ->select(
                $this->connection->quoteIdentifier('contentobject_id')
            )
            ->from($this->connection->quoteIdentifier('ezcontentobject_attribute'))
            ->where(
                $query->expr()->eq(
                    $this->connection->quoteIdentifier('id'),
                    ':fieldId'
                )
            )
            ->setParameter(':fieldId', $fieldId, PDO::PARAM_INT)
        ;

        $statement = $query->execute();

        return (int) $statement->fetchColumn();
    }