public function pop($queue = null) {
        if ($queue === null) { $queue = $this->queue; }
        $query = DB::table($this->table)->where('queue_name', $queue)
            ->where('status', 'pending')
            ->where('fireon', '<', time())
            ->orderBy('fireon', 'asc');
        if ($query->count() == 0) {return null;}
        $record = $query->first();
        return new Jobs\MysqlJob($this->container, $record->ID, $record);
    }