Unable to Fetch Firestore Data Using Nested Collections in Flutter

Question

I'm having trouble fetching data from Firestore using nested collections in a Flutter application. The data is structured as follows:

users/{userId}/tests/{testType}/test_set/{testSetId}

Image of data in firestore:

I am trying to retrieve all documents within the test_set collection for a specific test type. However, my queries are returning empty results, even though the data exists in Firestore. The Firestore security rules are set to allow read and write access for authenticated users.

users
  └── {userId}
        └── tests
              └── {testType}
                    └── test_set
                          └── {testSetId}
                                ├── correct_answers: int
                                ├── total_questions: int
                                └── timestamp: Timestamp

rules_version = '2';

service cloud.firestore {
  match /databases/{database}/documents {
    match /{document=**} {
      allow read, write: if request.auth != null;
    }
  }
}

Here is the relevant part of my Flutter code where I'm trying to fetch the data:

Future<List<Map<String, dynamic>>> _fetchTestResults() async {
    final user = FirebaseAuth.instance.currentUser;
    if (user == null) return [];

    print("UUID = " + user.uid);

    // Build the reference step by step and print debug information
    final usersRef = FirebaseFirestore.instance.collection('users');
    print('Users reference path: ${usersRef.path}');

    final userDocRef = usersRef.doc(user.uid);
    print('User document reference path: ${userDocRef.path}');

    final testsCollectionRef = userDocRef.collection('/tests/');
    print('Tests collection reference path: ${testsCollectionRef.path}');

    // final testResultsRef =
    //     testsCollectionRef.doc(testType).collection('test_set');
    // print('Test results reference path: ${testResultsRef.path}');

    // Fetch data
    final snapshot = await testsCollectionRef.get();
    print('Snapshot: ${snapshot.docs.length} documents');

    if (snapshot.docs.isEmpty) {
      print("Snapshot empty");
      return [];
    }

    return snapshot.docs.map((doc) {
      final data = doc.data();
      print('Document ID: ${doc.id}, Data: $data');
      return {
        'test_id': doc.id,
        'data': data,
        'timestamp': data['timestamp'] as Timestamp,
        'correct_answers': data['correct_answers'] as int,
      };
    }).toList();
  }

Logs showing 0 snapshots image below

But if instead I print the userRef.get() as snap shot I get output as below

final snapshot = await usersRef.get();
    print('Snapshot: ${snapshot.docs.length} documents');

Answer 1

Both of the document names in that tests subcollection are shown in italics in the Firebase console. This means that there are no actual documents at those locations, and the Firebase console only shows those IDs because there is content under them in the database.

If you want to load the document IDs are your code currently does, you'll have to make sure those documents in tests exist.

Also see:

• Firestore DB - documents shown in italics
• Why are non auto-generated document Ids are in italics in Firestore console?
• Firestore query returns no documents even though they are shown in the console in italics