title: Can I filter Multiple Fields in a Firestore search?
body: <p>I use Firestore database in my app.<br>
  Now, is it possible to search for a particular word in multiple fields?</p>
  
  <p>For example: Imagine a word like <em>"cheesecake"</em>. Now, I have 100 documents in collection and each document has 10 different fields.<br>
  Can I filter for the word <em>on <strong>all of the fields</em></strong>, so that it returns any document that contains the word <em>"cheesecake"</em> in <em>any of the fields</em>, in Flutter?</p>