Queries regarding firebase realtime database

Question

I am using the firebase realtime database in my android app. I only want the last entry inserted into the database and not an entire database sync.I am doing the following.

FirebaseDatabase.getInstance().getReference("reference").limitToLast(1).addValueEventListener(this);

Here's what I could not clearly understand :

1.When I do a limitToLast and add a listener, does it download the entire data from the database into the local copy and pass me a snapshot of the last entry or does it download only the last entry?

2.When I remove the listener , does the sync stop between the realtime database and the local data or the sync keeps happening but the onDataChange is not called?

3.The difference between removing the Value Event listener and going Offline.

Answer 1

When you call limitToLast() you create a Firebase Database query. Such a query only synchronizes the data that it matches, so in your example it only downloads the last item and invokes onDataChange with it. Then when somebody adds a new item, it invokes onDataChange again with the new last item.

Removing a listener stops the data synchronization.

Going offline temporarily stops data synchronization, until you call goOnline().