Number of reads from cloud_firestore

[tgbarker]

Imagine I have the following pseudo code :

  Stream<List<T>> list() {
      Query query = Firestore.instance.collection("items");
      return query.snapshots().map((snapshot) {
        return snapshot.documents.map((doc) {
          return standardSerializers.deserializeWith(serializer, doc.data());
        }).toList();
      });
  }

I listen to this stream somewhere in my code. Let's say this query returns 10 "items" the first time this is called for example. If I modify one of these documents directly in the firestore web interface (or elsewhere), the listener is fired and I have the impression another 10 reads are counted, even though I only modified one document. I checked in the usage tab of my cloud project.
Is this the case that 10 document reads are counted even if just one document is modified?

If the answer is yes, the next question would be "Imagine I wanted to have two calls to list(), one with orderBy "rating", another with orderBy "time" (random attributes), one of these documents changes, this would mean 20 reads for 1 update"? Either I am missing something or firestore isn't adapted for my use.

Is there any way to just retrieve the changed documents?

ref =>
firebase_database: ^4.0.0
firebase_auth: ^0.18.0+1
cloud_firestore: ^0.14.0+2

Thank you in advance.

[tgbarker]

https://stackoverflow.com/questions/63737857/what-is-the-read-count-for-realtime-listening-of-cloud-firestore-query-and-can-i/63738765#63738765