如何使用 flutter 更新 Firestore 中所有文档的单个字段？

Question

I have a 100 user documents in database, and I have to update one field to 0 in all documents. How do we do it?

Answer 1

Firestore doesn't offer a SQL-like "update where" command that updates everything at once, so you will have to:

1. Query for the documents to update
2. Iterate each DocumentSnapshot and get its DocumentReference object using the reference property
3. For each document, update the field with its new value

Answer 2

Try doing the following

1. Query the documents to update
2. Go through each DocumentSnapshot and get its DocumentReference object using the reference property and for each document, update the field with its new value

    void updateNotificationCount() async {
        FirebaseUser _currentUser = await FirebaseAuth.instance.currentUser();
        String authid = _currentUser.uid;
        var snapshots =
            activityFeedRef.document(authid).collection('feedItems').snapshots();
        try {
          await snapshots.forEach((snapshot) async {
            List<DocumentSnapshot> documents = snapshot.documents;
    
            for (var document in documents) {
              await document.reference.updateData(<String, dynamic>{
                'seen': true,
              });
            }
          });
        } catch (e) {
          print(e.toString());
        }
      }

The code above simply updates all unread notification from false to true immediately the user clicks on the notification tray

Answer 3

As @Doug mentioned there's no direct way, you'll have to query the data, get the DocumentReference from QueryDocumentSnapshot and invoke update on it.

var collection = FirebaseFirestore.instance.collection('collection');
var querySnapshots = await collection.get();
for (var doc in querySnapshots.docs) {
  await doc.reference.update({
    'single_field': 'newValue',
  });
}