title: Will push notification be collapsed if collapse_key not passed in payload?
body: <p>As mentioned <a href="https://developers.google.com/cloud-messaging/concept-options" rel="nofollow noreferrer">here</a>:</p>
  
  <blockquote>
    <p>If the device is connected but in doze mode, a low priority message is stored by GCM until the device is out of doze mode. And that's where the collapse_key flag plays a role: if there is already a message with the same collapse key (and registration token) stored and waiting for delivery, the old message will be discarded and the new message will take its place (that is, the old message will be collapsed by the new one). However, if the collapse key is not set, both the new and old messages are stored for future delivery.</p>
  </blockquote>
  
  <p>I wanted to understand what will be the behaviour if <code>collapse_key</code> is not passed in the payload?</p>
  
  <p>It is also mentioned <a href="https://firebase.google.com/docs/cloud-messaging/concept-options#delivery_options" rel="nofollow noreferrer">here</a>:</p>
  
  <blockquote>
    <p>Except for notification messages, all messages are non-collapsible by default.</p>
  </blockquote>
  
  <p>Does that mean all push notifications are  collapsible by default and user will get only one notification, if there are multiple messages sent to him when he is offline?</p>