Disable the first query snapshot when adding a snapshotListener

Question

Firestore realtime updates documentation here

Here is the comment you can find in the documentation.

Important: The first query snapshot cont

Answer 1

AtomicBoolean isFirstListener = new AtomicBoolean(true);

commentListener = getLectureCommentsCollecReference(courseId, lectureId)
                .addSnapshotListener((queryDocumentSnapshots, e) -> {
                    if (isFirstListener.get()) {
                        isFirstListener.set(false);
                        //TODO Handle the entire list. 
                        return;
                    }
                    for (DocumentChange dc : queryDocumentSnapshots.getDocumentChanges()) {
                        switch (dc.getType()) {
                            case ADDED:
                                sendCommentAddedEvent(DataParser.parseComment(dc));
                            case MODIFIED:
                                sendCommentUpdatedEvent(DataParser.parseComment(dc));
                                break;
                        }
                    }
                });

This is one way of doing it. I use this inside a comment feature for listening to new comment Added as well as if comments are modified.

Answer 2

There is no way to suppress getting the initial data.

Depending on the use-case, you may want to attach your listener to a subset of the data. E.g. if you have an append-only scenario (such as chat), you can start listening for data that was modified after "now".