title: Maximum size of a document in firestore?
body: <p>I want create a document that containing about 20 million objects.</p>
  
  <p>The structure like that:</p>
  
  <pre><code>documentID
  ---- key1
  -------- object1
  -------------name: "test1"
  -------------score: 123
  </code></pre>
  
  <p>I don't know the limitation of a document size in firestore, so can you help me any reference or information about that?
  Thanks!</p>