Can I use the same RoomDatabase object from multiple threads on Android?

Question

I'm using the Room persistence library on Android. Currently, I have some extra synchronization code each time I access the database. I want to know if this code is necessary.

I currently access the database as a singleton. This is how I am currently inserting objects into the DB:

    // Insert values into DB
    final AppDatabase db = AppDatabase.get(this);
    AsyncTask.execute(new Runnable() {
        @Override
        public void run() {
            synchronized (db) {
                for (WorkOrder wo : workOrderList) {
                    db.workOrderDao().insertAll(wo);
                }
            }
        }
    });

Do I need to have the insertion code in a synchronized block?

Answer 1

RoomDatabase wraps the standard SQLiteDatabase, which is fairly thread-safe, with all work being done in transactions.

I would worry less about synchronized and more about transactions, as right now, this work is being done in N transactions (one per WorkOrder). I would have an insertAll(List<WorkOrder>), so you can perform this in one transaction. Or, if for whatever reason that's impractical, move your loop into the @Dao class in its own method, with a @Transaction annotation, to indicate that the entire method should be performed in a single transaction.