firebase google or query support or any alternative solution

Question

We have just started exploring firebase for our new app. The app basically needs chat between users and Group chat.

For the chat application we are creating: MessageThread(id, User:userA, User:userB, UserGroup:group, Array:deletedBy, ...)

The main problem is firebase doesn't support OR queries and IN queries, which I need in my use-case. For example:

Dummy query to access user's conversations list: fetch MessageThread(s) where (currentUser.id==userA.id) OR (currentUser.id==userB.id) OR (currentUser.id IN group.members)

I am missing something to understand Firebase? What is the other alternative way to design our database to solve this problem?

score 3 · Accepted Answer · answered Jun 15 '16 at 14:58

In NoSQL you will have to model the data for the way your app wants to use it. So if you need a list of the conversations that the user is part of, you should keep that list in your database:

/conversationMessages
    $conversationId
        $messageId
            text: "Hello world"
            sender: "uid of sender"
            name: "name of sender"
/userConversations
   $uid
     $conversationId1: true
     $conversationId2: true

With this you can easily look up the list of conversations that each user is a part of and then load the messages for one of them. You'll probably also want to keep a separate list of the metadata for each conversation:

/conversationMetadata
    $conversationId
        lastUpdated: timestamp (set with ServerValue.TIMESTAMP)
        title: "name of our chat room"

That way you can show the list of conversations for a user by loading their conversation ids and then loading the metadata of each conversation:

var ref = database.ref().child("userConversations").child(auth.uid);
ref.on('child_added', function(conversationKey) {
    var conversationRef = database.ref().child("conversationMetadata").child(conversationKey.key);
    conversationRef.once('value', function(metadataSnapshot) {
      console.log(metadataSnapshot.val());
    });
});

Trying to map SQL knowledge onto a NoSQL database leads to a difficult learning experience. I highly recommend reading the relevant section of the Firebase documentation and this article about NoSQL data modeling.

Thank you, one more question: Is there any support of making references in firebase? For example: I want to save user's object in conversation, so that I can show user's name and photo on the conversation list screen. — iMemon, Jun 19 '16 at 20:43
There are no managed foreign key references. But it's very common to have (unmanaged) references. See the section of the documentation on [creating data that scales](https://firebase.google.com/docs/database/android/structure-data#fanout). — Frank van Puffelen, Jun 19 '16 at 22:26
In my senerio, I have group/user chat and chat name & image is fetched from that group/user And I can't denormalize it because user has the option to change it anytime. So from your mentioned approach, I can have a table /conversationMetadata where I will a reference of user/group. Now the problem is for fetching a conversation list (as explained in your mentioned above code): First I am fetching userConversations then I am fetching conversationMetadata for every conversation and then I need to fetch userData or groupData (to get name/image). Don't u think it will be too slow? Please help. — iMemon, Jun 21 '16 at 01:40
See http://stackoverflow.com/questions/35931526/speed-up-fetching-posts-for-my-social-network-app-by-using-query-instead-of-obse/35932786#35932786 — Frank van Puffelen, Jun 21 '16 at 02:10

firebase google or query support or any alternative solution

1 Answers1