Firestore duplicate verification conditions

Question

My Firestore database looks like this

For documents I use dynamic IDs. I do not use the user ID in the path, it is stored in the field. The fields have the values user and active.

How can I prevent adding new entries if, for example, the user 37870283 already has an active = true?

Answer 1

There is no way to ensure the uniqueness of a field value in Firestore security rules. The only ways to ensure uniqueness are:

1. Use the thing that needs to be unique as the document ID.
2. Perform all writes from a single, trusted process (like Cloud Functions), and use transactions there.

Also see:

• Cloud Firestore: Enforcing Unique User Names
• Prevent duplicate entries in Firestore rules not working
• Firestore security rule to check if character username already exists

And more from this list