How to get all documents belong to specific subcollection using Flutter and Firestore

Question

Let's say, I have this kind of architecture in Firestore;

   - Users (collection)
     - User A (document)
       - Notes (collection)
         - Note A (document)
         - Note B (document)
         - Note C (document)
     - User B (document)
       - Notes (collection)
         - Note D (document)
         - Note E (document)
         - Note F (document)

And I want to get all notes of all users' (Note A,B,C,D,E,F for this example)

How can I achieve that in Flutter?

Answer 1

You need to use a Collection Group query as follows:

QuerySnapshot snapshot = await Firestore.instance.collectionGroup('Notes').get();

As explained in the doc :

A collection group consists of all collections with the same ID. By default, queries retrieve results from a single collection in your database. Use a collection group query to retrieve documents from a collection group instead of from a single collection.