title: Why the documents (that have further sub collection) size is 0 when you call .collection("collName"). get()?
body: <p>I have a similar problem as this question <a href="https://stackoverflow.com/questions/52614242/why-is-firestore-documentsnapshot-data-size-always-zero">question</a>, but no one has answered yet.  I have a collection that has documents and those documents have further collections. When I try to get these documents I receive 0 documents. <a href="https://i.stack.imgur.com/ZCsZO.png" rel="nofollow noreferrer">database image</a></p>
  <p>Code</p>
  <pre><code>db.collection(&quot;teachers&quot;).document(&quot;irfany&quot;).collection(&quot;OpenAssignments&quot;).
          get().addOnCompleteListener(new OnCompleteListener&lt;QuerySnapshot&gt;() {
      @Override
      public void onComplete(@NonNull Task&lt;QuerySnapshot&gt; task) {
          if (task.isSuccessful()) {
              Log.d(&quot;getdocumentSize&quot;, task.getResult().size() + &quot; =&gt; &quot;);
  
              for (QueryDocumentSnapshot document : task.getResult()) {
  
              }
          } else {
              Log.d(&quot;Error&quot;, &quot;Error getting documents: &quot;, task.getException());
          }
      }
  });
  </code></pre>
  <p><strong>Output</strong>  D/getdocumentSize: 0 =&gt;</p>