clearIndexedDbPersistence

Clears the persistent storage. This includes pending writes and cached documents.

Must be called while the Firestore instance is not started (after the app is terminated or when the app is first initialized). On startup, this function must be called before other functions (other than initializeFirestore or {@link (getFirestore:1)})). If the Firestore instance is still running, the promise will be rejected with the error code of failed-precondition.

Note: clearIndexedDbPersistence() is primarily intended to help write reliable tests that use Cloud Firestore. It uses an efficient mechanism for dropping existing data but does not attempt to securely overwrite or otherwise make cached data unrecoverable. For applications that are sensitive to the disclosure of cached data in between user sessions, we strongly recommend not enabling persistence at all.