title: How to check if multiple documents exist
body: <p>Is there such a query that gets multiple fields, and returns which of these exists in the collection?
  For example, if the collection has only:</p>
  
  <pre><code>{id : 1}
  {id : 2}
  </code></pre>
  
  <p>And I want to know which of <code>[{id : 1} , {id : 3}]</code> exists in it, then the result will be something like <code>[{id : 1}]</code>. </p>