private function markAsActive($workerID = 0)
    {
        if ($workerID == 0) {
            $query = $this->pdo->prepare(<<<SQL
UPDATE robotstxt__cache1
SET worker = NULL
WHERE base = :base AND worker = 0;
SQL
            );
            $query->bindValue('base', $this->base, \PDO::PARAM_STR);
            return $query->execute();
        }
        return true;
    }