Consider adding .indexOn for Firebase
<p>I have a Firebase database as :</p>

<pre><code> "requested_rides" : {
"2016-10-04" : {
  "-KT9F_8DJHmKj33PW70w" : {
    "added_on" : 1475493385140,
    "code" : "AQZ66I4QP4",
    "date_of_ride" : "2016-10-04 AD 04:22 AM GMT+05:45",
    "day" : "Tomorrow",
    "dropoff_coordinate" : "27.6953541,85.2965062",
    "dropoff_location" : "Chunne Pakha",
    "fullname" : "bhaskarraj93@gmail.com",
    "offered_by" : "v1tENP2TaUVHaZFhSGuZ4M6cJJU2",
    "pickup_coordinate" : "27.716454540107783,85.32458111643793",
    "pickup_location" : "Kuber Plazza, Kathmandu 44600, Nepal",
    "seats" : "2",
    "share" : "578",
    "time" : "04:22 AM",
    "vechile_type" : "Bike"
  }
},
</code></pre>

<p>I have added rules to the database but I am getting this error</p>

<p>Consider adding <code>".indexOn": "code"</code> at /requested_rides/2016-11-23 to your security and Firebase rules for better performance</p>

<p>The rule that I defined is </p>

<pre><code>"rules":{
    ".read":true,
    ".write":true,
    "requested_rides":{
        ".indexOn":"code"
    }
}
</code></pre>