How to Firebase Firestore realtime update Only new data added to collect?

Question

For example : WorkingTask App. I use Redux - React

Structure

JobOrders (collections) / eachJob (docu)

- the app is allow only insert new JOB.
- the whole day has 500-1000 Jobs.
- the all jobs must be used to recompute the report realtime.  
- clear data once every midnight.

I know how to fetch and listen-realtime callback for the whole. but the problem is the callback function must recompute the whole documents (maybe 300-1000 Jobs every-time when a new JOB arrived.)

This is I want:

- every new JOB arrived only new data in callback then I can recompute in REDUX.  

- and prevent for some data is delay due to internet network connection.

I come across with : to listen limit to 1 and sortBy timestamp 'desc'.

But the problem is if some JOB are delay due to network connection, it will not call in callback.

Answer 1

I'm looking for this problem also but now i find out onAddSnapshotListener // as real time update. only get the new or changed documents

https://youtu.be/3aoxOtMM2rc?t=195

Try to watch the whole series

Answer 2

I think Firestore querySnaptshot should have Information for documents changed

for example Node.js

let observer = db
  .collection('cities')
  .where('state', '==', 'CA')
  .onSnapshot(querySnapshot => {
    querySnapshot.docChanges().forEach(change => {
      if (change.type === 'added') {
        console.log('New city: ', change.doc.data());
      }
      if (change.type === 'modified') {
        console.log('Modified city: ', change.doc.data());
      }
      if (change.type === 'removed') {
        console.log('Removed city: ', change.doc.data());
      }
    });
  });