protected function fetchUserId($fieldId)
    {
        $query = $this->dbHandler->createSelectQuery();
        $query
            ->select(
                $this->dbHandler->quoteColumn('contentobject_id')
            )
            ->from($this->dbHandler->quoteTable('ezcontentobject_attribute'))
            ->where(
                $query->expr->eq(
                    $this->dbHandler->quoteColumn('id', 'ezcontentobject_attribute'),
                    $query->bindValue($fieldId)
                )
            );

        $stmt = $query->prepare();
        $stmt->execute();

        return $stmt->fetchColumn();
    }