Firebase & Flutter how to structure my data and how avoid high costs by checking if a username already exists

Question

currenty when somebody registers in my app, im providing an Input field which returns if the entered username already exists in the database.

Future getUserName(String userNameFieldInput) {
    print('userNameFieldInput: $userNameFieldInput');
    return FirebaseFirestore.instance
        .collection('usernames')
        .doc(userNameFieldInput)
        .get()
        .then((value) => value.exists ? true : false)
        .catchError((error) => print(error));
  }

Im returning true or false and thats totally fine. Im not sure if my database structure is fine for that. I would love to have some recommendations on here. Also how many reads do we have here? IM using the Firestore.

MyDatabase
 |
 ---Users
 |   |
 |    ---THE_USERS_UID
 |         |
 |         |--name: "marcel"
 |         |
 |         |---gender: "male"
 |         |...
 |
 ---usernames
     |
     ---marcel
          |
          |---uid: "THE_USERS_UID"

Frank van Puffelen · Accepted Answer · 2021-03-14 15:15:11Z

1

Yup, this looks fine to me.

If you want something to be unique, you should use that as the ID of your documents in a collection, which you're doing in your usernames collection.

That also ensures that you only need to read/check for the existence of a single document to determine if a username is already in use, which is the minimum number of document reads that is possible for such an operation.

answered Mar 14, 2021 at 15:15

Frank van Puffelen

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