title: Difference Between Firestore Set with {merge: true} and Update
body: <p>In <strong>Cloud Firestore</strong> there are three write operations:</p>
  <ol>
  <li><code>add()</code></li>
  <li><code>set()</code></li>
  <li><code>update()</code></li>
  </ol>
  <p>In the docs it says that using <code>set(object, { merge: true })</code> will merge the given object with the existing document.</p>
  <p>The same happens when you use <code>update(object)</code>... so what is the difference? It seems strange that google would duplicate functionality like this.</p>