How to prevent race condition when save data on Drift

[rizaldi-wiratama]

Hello everyone, firstly thank you so much for this awesome persistence database

I have some question regarding how to prevent race condition when save data on Drift

There's case that i have Order class that already implements Insertable<Order> (custom row class) that consist of several field.
When saving an order using Manager API , first I check if field dateLastActivity is already changed or not
if already changed then we throw an error "Order already changed"
but if not already changed then we update date last activity & save order with mode replace just like these code

  ///Save order by check first if local order already exist and date last activity is changed
  ///- if date last activity is changed then throw error
  ///- if not changed then update date last activity & save order with mode upsert
  saveOrder(Order updatedOrder) async {
    ///Get local order, can return null if order is not found with filter by [uuid]
    Order? localOrder = await database.managers.orders.filter((f) => f.uuid(updatedOrder.uuid)).getSingleOrNull();

    ///Check if date last activity is changed or not
    if(localOrder != null && localOrder.dateLastActivity != updatedOrder.dateLastActivity) throw("Order already changed");

    ///Update date last activity before save
    updatedOrder.dateLastActivity = dateFormat.format(DateTime.now());
    
    ///Save order with mode replace so it will behave like upsert (update/insert)
    await database.managers.orders.create((o) => order, mode: InsertMode.replace);
  }

This saveOrder function can be called on several service

My question, when there's case several service access saveOrder function with same order at the same time, is this may lead to race condition?
If yes, then how to ensure that this not lead to race condition?

I already research some way to prevent race condition such as Acquiring a Read Lock on SQLite in here , is Drift also support like this?

and I already know there's onConflict callback inside database.managers.orders.create , but how to check if field dateLastActivity is changed or not inside that callback? , is there any way that we can check field dateLastActivity & update that field before save order? or do we need Transaction for this case?

Thanks in advance

[simolus3]

Yes! You can run multiple statements atomically (with an implicit lock on the database) by using transactions:

saveOrder(Order updatedOrder) async {
  await database.transaction(() async {
    Order? localOrder = await database.managers.orders....;
    // Rest of your update logic here
  })
}

Transactions essentially behave as if all their statements inside ran as one (which also means that no concurrent invocation of saveOrder can cause race conditions).

[rizaldi-wiratama]

Thank you so much @simolus3 for the answer , I will try to do it later using transactions 👍