How to enforce Uniqueness in a Property of a document field in Google Cloud Firestore

Question

I have the following data as shown in the image. I want to make sure that the username field is unique. How can I enforce that? Bear in mind that my document id is already unique and I don't want to use my username as the document ID

Answer 1

There is no way to enforce unique values of fields in Firestore. The only uniqueness you can guarantee is the document IDs within a collection, so the solution is to create a new collection where the user names are used as document IDs.

This has been discussed a few times before, so I recommend checking out:

• Firestore security rule to check if character username already exists
• Check a document field for a specific value in Cloud Firestore
• I want to make unique usernames in firebase/firestore, which shows some of the relevant security rules.
• Cloud Firestore: Enforcing Unique User Names
• Firestore unique index or unique constraint?, a more complete write-up with code and rules samples.
• Cloud Firestore: Enforcing Unique User Names