How to get multiple children with their IDs in one query

Question

I'm trying to add chat feature to an Android App with Firebase Realtime DB as storage.

My schema is something like this,

conversation: {
  conversation_id_generated_by_firebase: {
    last_message: {
      message: "hehe"
      type: "text"
      attachments: {0: "url", 1: "url"}
      likes: {0: "uid1", 1: "uid2"}
      created_at: 1245789898
    },
    messages: {
      m1: {
        message: "hehe"
        type: "text"
        attachments: {0: "url", 1: "url"}
        likes: {0: "uid1", 1: "uid2"}
        created_at: 1245789898
      }, m2: {}, m3: {}, m4: {}
    },
    read_till: {
      uid1: 14567894229
      uid2: 14567894228
    },
    created_at: 1456789329
    updated_at: 1456789429
  },
}

Now, How can I fetch multiple conversations with ids in one query/call?

score 5 · Answer 1 · edited May 23 '17 at 11:48

There is no Firebase equivalent to SQL's SELECT * WHERE id IN (1,2,3). In Firebase you'll retrieve each item separately.

This is not nearly as slow as most developers think, since Firebase can efficiently pipeline such requests over a single connection. See my answer here for a longer explanation (and some ASCII art): Speed up fetching posts for my social network app by using query instead of observing a single event repeatedly

score 0 · Answer 2 · answered Nov 03 '16 at 13:31

By retrieving ID do you mean you want to retrieve "conversation_id_generated_by_firebase", If yes, i have implemented somewhat similar thing, have modified code as per your DB details. If you could provide some code from what you have tried i can help you further.

    ArrayList<String> keyList = new ArrayList<>();

    // i am assuming you have Chat Object for each conversation
    ArrayList<Chat> chatList = new ArrayList<>();

    myRef = database.getReference().child("conversation");
    ValueEventListener chatListener = new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
        //will be called every time a new conversation is added

          if(dataSnapshot != null){
              for (DataSnapshot postSnapshot : dataSnapshot.getChildren()) {  
                String key = postSnapshot.getKey();

                //store key(your id) in array list
                keyList.add(key);


                //now i am assuming you have an object of chat message
                Chat chat = postSnapshot.getValue(Chat.class);

                //add all conversation to chatList ArrayList
                chatList.add(chat);
               }
           }
        }



        @Override
        public void onCancelled(DatabaseError databaseError) {
         //handle error incase something fails
        }
    };
    myRef.addValueEventListener(chatListener);

How to get multiple children with their IDs in one query

2 Answers2