NoSQL data base design for firebase chat

Question

I am designing a chat app with the help of firebase but I am struck with the database design for the same. I have read the following link provided by firebase structure data for app

My current approach:

"messages" : {
  "-Kkiyu4zSKQAzu3MxpGe": {
    "recId" : 1994,
    "senderId" : 9,
    "senderName" : "Alex",
    "text" : "Hello",
    "time" : "2017-05-22T12:37:41+0530"
  },
  "-Kkiyw1yVTbR_wDFFiuA" : {
    "recId" : 9,
    "senderId" : 1994,
    "senderName" : "Ted",
    "text" : "Hi",
    "time" : "2017-05-22T12:37:49+0530"
  },
  "-KkiywFENy__tCHuuuom" : {
    "recId" : 1994,
    "senderId" : 9,
    "senderName" : "Alex",
    "text" : "What's up?",
    "time" : "2017-05-22T12:37:50+0530"
  },
  "-KkiyxDjsUIXBlM0Cn3R" : {
    "recId" : 9,
    "senderId" : 1994,
    "senderName" : "Ted",
    "text" : "All good",
    "time" : "2017-05-22T12:37:54+0530"
  }

similarly, I have user JSON structure and in that structure, I am having 3 types of users which are as follows

1. Branch Manager 2. Delivery boy 3. Admin

"users" : {
  "9" : {
    "empId" : 9,
    "isOnline" : false,
    "name" : "Alex",
    "userType" : "M"
  },
  "1994" : {
    "branchId" : 9,
    "empId" : 1994,
    "isOnline" : false,
    "name" : "Ted",
    "userType" : "D"
  },
  "25" : {
    "empId" : 25,
    "isOnline" : false,
    "name" : "Tim",
    "userType" : "A"
  }
}

and my listeners in application are as follows:

sendReference.observe(.childAdded, with: { (snapshot) in
        if let data = snapshot.value {
            let message = RCMessage(object: data)
                message.Id = snapshot.key
            let dbManager = RCPersistencyManager()
                dbManager.add(message: message)
        }
    })

receiveReference.observe(.childAdded, with: { (snapshot) in
        if let data = snapshot.value {
            let message = RCMessage(object: data)
            message.Id = snapshot.key
            let dbManager = RCPersistencyManager()
            dbManager.add(message: message)
            dbManager.update(userwithMessage: message)
        }
    })

i added the listners on the my senderId and my recieverId which i thought was cleaver as i will be recieving messges only that are either send by or directed towards me.

sendReference = companyReference.child("messages").queryOrdered(byChild: "senderId").queryEqual(toValue: Int(RCDataManager.get(stringforKey: "RCUserID")!))

receiveReference = companyReference.child("messages").queryOrdered(byChild: "recId").queryEqual(toValue: Int(RCDataManager.get(stringforKey: "RCUserID")!))

but now the bigger problem arrived i attach these listeners as soon the app is in foreground now the data I receive is every single child created under the following query I do maintain a local database for app but i don't want to get all the children again and again as when the number of children will be more than 200 or say 300 it takes time to sync the database which decreases my app's performance I want to get only the new messages under the queries and I know this design is not good to get that really looking forward to good answers.

Thanks in advance

Christi

Answer 1

the data I receive is every single child created under the following query I do maintain a local database for app but i don't want to get all the children again and again as when the number of children will be more than 200 or say 300 it takes time to sync the database which decreases my app's performance I want to get only the new messages under the queries

Your question has a lot to unpack, but that just shows your detail oriented. Attempting to unpack the issue, it seems you're really just looking to limit your query results to the most recent.

In order to do that, look into filtering your data

Here's what I would do if I were you in almost psuedo code:

1) Initial population of local cache of messages.
2) On subsequent opens, query your local cache for the 
    newest message and check the `time` at which it was created
3) In your queries to Firebase, add the queryStartingAtValue and pass it your last synced time and you'll only receive new messages.

Without knowing what your UI looks like, it's hard to say the feasibility of limiting the number of messages you download, as you would need some kind of "load more" indicator to do that seamlessly. The approach would be identical to the initial loads.

Anarchist