Firestore: How to get random documents in a collection

Question

It is crucial for my application to be able to select multiple documents at random from a collection in firebase.

Since there is no native function built in to Fireb

Answer 1

Ok I will post answer to this question even thou I am doing this for Android. Whenever i create a new document i initiate random number and set it to random field, so my document looks like

"field1" : "value1"
"field2" : "value2"
...
"random" : 13442 //this is the random number i generated upon creating document

When I query for random document I generate random number in same range that I used when creating document.

private val firestore: FirebaseFirestore = FirebaseFirestore.getInstance()
private var usersReference = firestore.collection("users")

val rnds = (0..20001).random()

usersReference.whereGreaterThanOrEqualTo("random",rnds).limit(1).get().addOnSuccessListener {
  if (it.size() > 0) {
          for (doc in it) {
               Log.d("found", doc.toString())
           }
} else {
    usersReference.whereLessThan("random", rnds).limit(1).get().addOnSuccessListener {
          for (doc in it) {
                  Log.d("found", doc.toString())
           }
        }
}
}