Query a specific child node in all instances of a parent node in Firebase

Question

I\'m trying to figure out how, if possible, to query a specifically named child node in all instances of a parent node in Firebase. It can be assumed that all parent nodes queri

Answer 1

Firebase world is quite different!

When such scenarios come you have to think to redesign your database structure, In your case uid is unique identifier so is displayName- speaking technically.

You will have to maintain additional data like:

{
  users: {
    uid: {
      displayName: "stringOfSomeKind"
    }
    uid2: {
      displayName: "moreStrings"
    }
    uid3: {
      displayName: "evenMoreStrings"
    }
    ... 
  }
 displayNames: {
        "display_name": "uid",
        "display_name2": "uid2",
        "display_name3": "uid3"
     ...      
 }
}

Happy Helping!

Answer 2

When you load a node from Firebase, you also get all data under that node. Assuming that you have more data per user than just their display name, that can indeed lead to needlessly loaded data.

If you only want to load a list of display names, you should indeed store a list of display names.

{
  displayNames: {
    "stringOfSomeKind": "uid",
    "moreStrings": "uid2",
    "evenMoreStrings": "uid3"
  }
}

If you come from a background of relational/SQL databases, this may seem unnatural at first. For me it helped to realize that these structures are indexes, same as the "index by displayName" that you might add to your relational database. The difference is that in NoSQL/Firebase it is your code that maintains the index, while in most RDBMSs such indexes are maintained by the system.