android - Firebase mimicing WHERE IN

Question

Given the date model provided below, after a user logs in and retrieves their data, they can also get a list of their friends.

However, in order to now attain details of those two friends by ids fdb17f3a-7b7d-4aa5-9a0b-b9fb33c349de and a96da7b1-7c4e-44bc-b82e-fc75bed52bcd, at present, the most efficiently operation appears to simply be to loop through the urls, in such a way as:

for singleFriendID in allFriendIds

    firebase.com/[my_db_name]/users/{singleFriendID} 

end

but even that has its major limitations, if say you want a list of usernames of your 40 friends, you now need 40 individual, specific calls, to the server...

How can I efficiently lookup data within Firebase instead of dumping all the friend details to their phone?

Firebase schema:

{  
   "users":{  
      "99e4989b-a046-4c5f-9478-5ebd8bdc3ded":{  
         "email":"person@gmail.com",
         "friends":{  
            "fdb17f3a-7b7d-4aa5-9a0b-b9fb33c349de":{  
               "confirmed":true,
               "selfSendRequest":false,
               "timeInvited":"2016-02-21 08:49:31"
            },
            "a96da7b1-7c4e-44bc-b82e-fc75bed52bcd":{  
               "confirmed":true,
               "seldSendRequest":false,
               "timeInvited":"2016-02-21 08:49:31"
            }
         },
         "password":"aPassword",
         "phoneNumber":"16144444444",
         "username":"person2"
      }
      "a96da7b1-7c4e-44bc-b82e-fc75bed52bcd": {
      ...
      ...
   }
}

Answer 1

Waitting for answers