How to add index rules for Firebase database?
<p>I keep getting firebase messages on console regarding to add indexOn for user 4321 at chat rules. Below is my database.</p>

<p><a href="https://i.stack.imgur.com/trZet.png" rel="noreferrer"><img src="https://i.stack.imgur.com/trZet.png" alt="enter image description here"></a></p>

<p>And my rules in firebase is like:</p>

<pre><code>{
  "rules": {
    ".read": "auth != null",
    ".write": "auth != null",
    "users": {
      ".indexOn": ["name", "email","uid"],
      "$uid": {
        ".write": "$uid === auth.uid"
      }
    },
    "chats": {
      "$key": {
        ".indexOn": ["uid"] 
      }
    }
   }
}
</code></pre>

<p>I'm not sure why the indexing not working. And how can I improve indexing for overall database?</p>