CollectionReference.where helps quering firestore db.

https://firebase.google.com/docs/reference/js/firebase.firestore.CollectionReference#where

For instance using "array-contains" to find docs with the same field.

Looking at v6 documentation it is not yet implemented.

https://invertase.io/oss/react-native-firebase/v6/firestore/reference/collectionreference

Thank you very much.