title: Laravel Notification duplicate error with more than one notification via (database,email)
body: <p>I have more than 1500 users and sending them a notification via Mail and Database to remind them something every week using cron and supervisor.</p>
  
  <p>My queue config:</p>
  
  <pre><code>'database' =&gt; [
      'driver' =&gt; 'database',
      'table' =&gt; 'jobs',
      'queue' =&gt; 'default',
      'retry_after' =&gt; 90,
  ],
  </code></pre>
  
  <p>My Supervisor config:</p>
  
  <pre><code>[program:run-cron]
  process_name=%(program_name)s_%(process_num)02d
  command=php /var/www/html/projectName/artisan queue:work database --sleep=3 --tries=3  --timeout=50 --queue=default,reminder
  autostart=true
  autorestart=true
  user=www-data
  numprocs=6
  redirect_stderr=true
  stdout_logfile=/var/www/html/projectName/storage/logs/supervisor.log
  </code></pre>
  
  <p>Code at notification:</p>
  
  <pre><code>class UserReminderNotification extends Notification implements ShouldQueue
  {
      use Queueable;
      public $job,$days,$settings;
      /**
       * Create a new notification instance.
       *
       * @return void
       */
      public function __construct($data)
      {
          $this-&gt;queue="reminder";
          $this-&gt;user = $data['user'];
      }
  
      /**
       * Get the notification's delivery channels.
       *
       * @param  mixed  $notifiable
       * @return array
       */
      public function via($notifiable)
      {
          return array('database','mail');
      }
  
      /**
       * Get the mail representation of the notification.
       *
       * @param  mixed  $notifiable
       * @return \Illuminate\Notifications\Messages\MailMessage
       */
      public function toMail($notifiable)
      {
          $title = 'Reminder Title';
  
          return (new MailMessage)
              -&gt;subject($title)
              -&gt;view(
                  'user.reminder',
                  array(
                      'user' =&gt; $this-&gt;user,
                  )
              );
      }
  
      /**
       * Get the array representation of the notification.
       *
       * @param  mixed  $notifiable
       * @return array
       */
      public function toArray($notifiable)
      {
          return [
              'type' =&gt; 'user',
              'name' =&gt; $this-&gt;user-&gt;name,
              'messsage' =&gt; 'Reminder message';
          ];
      }
  }
  </code></pre>
  
  <p>Error What I am getting at failed job:</p>
  
  <blockquote>
    <p>PDOException: SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry '3fee38fc-8e1f-4212-9e96-12c4af1510c4' for key 'PRIMARY'</p>
  </blockquote>
  
  <p>What I am missing.retry_after is already greater than --timeout as you can see.</p>
  
  <p>I think on mail failing,when supervisor try once again at that time it again do entry for that database notification.Weird is that,it is not coming for all.</p>