title: How to make a subdocument have two parent documents in mongodb?
body: <p>I'm using <code>mongoose</code> with <code>Node.js</code> for an application. I have a <code>Document</code> class, which has a <code>Review</code> subdocument. I also have a <code>User</code> class.</p>
  
  <p>I want the user to be able to see all the reviews they've done, while I also want the <code>Document</code> to be able to easily get all of its reviews. Searching through all the documents and all their reviews to find ones matching a user seems horribly ineffecient. So, how do I allow the <code>Review</code> to be owned by both a <code>Document</code> and a <code>User</code>?</p>
  
  <p>If this is impossible, how else can I <strong>efficiently</strong> have two documents know about one subdocument.</p>