Usage of equalTo("value","key") in Firebase?

Question

Here is the following data structure :

{
  "list" : {
    "-K4YlfoWHZqPyWONv68Y" : {
      ".priority" : -1.449077948445E12,
      "date" : 1449077948445,
      "id" : "0",
      "name" : "Name_0"
    },
    "-K4YlfoWHZqPyWONv68Z" : {
      ".priority" : -1.449077948445E12,
      "date" : 1449077948445,
      "id" : "1",
      "name" : "Name_1"
    },
    "-K4YlfoWHZqPyWONv68_" : {
      ".priority" : -1.449077948445E12,
      "date" : 1449077948445,
      "id" : "0",
      "name" : "Name_2"
    },
    "-K4YlfoWHZqPyWONv68a" : {
      ".priority" : -1.449077948445E12,
      "date" : 1449077948445,
      "id" : "1",
      "name" : "Name_3"
    },
 ...
}

I need to only get item where id is "0";

The following is working :

final Firebase ref = new Firebase("https://millezim-test.firebaseio.com/").child("list");

ref.orderByChild("id").equalTo("1").addValueEventListener(new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        for (DataSnapshot d : dataSnapshot.getChildren()) {
            Model m = d.getValue(Model.class);
        }
    }

    @Override
    public void onCancelled(FirebaseError firebaseError) {

        }
});

But not this one, why ?

ref.equalTo("1","id").addValueEventListener(new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        for (DataSnapshot d : dataSnapshot.getChildren()) {
            Model m = d.getValue(Model.class);
        }
    }

    @Override
    public void onCancelled(FirebaseError firebaseError) {

        }
});

Did I misunderstand that equalTo("value","key") is to use without reordering By something ?

Answer 1

The Firebase documentation for equalTo says this about the (optional) key parameter:

The child key to start at, among the children with the previously specified priority. This argument is only allowed if ordering by priority.

Since you're not ordering by priority, you'll need to specify the child with an explicit call to orderByChild().