android - Sum firebase data efficiently up

Question

I have an app where I have up to a few thousand entries in a firebase table. Now someone is connecting to this table and I need to count and sum these items up.

-itemlist
|
--1
  |-x:2
--2
  |-x:4

and so on. A user can connect at any time (meaning he never saw this table before) and another user can change some value at any given time or add values.

Now if I try and add a ValueEventListener to "itemlist" it works if there is no new data but as soon as I connect to a new database with 1000 entries or so the listener calls for every one of these 1000 entries.

I tried with onChildlistener but this calls the on ChildItem added for every item extra on the first time. This takes over 2 minutes sometimes.

Is there a way to get the whole database once, calculate it and then only listen for changes?

Answer 1

Waitting for answers