account_id=record.account_id
current_balance=record.balance
new_balance=current_balance + 5
Account |> where(id: ^account_id) |> update(set: [balance: new_balance]) |> Repo.update_all([])
This is still a read, modify, write. This will not work safely. You must use inc: so that the change happens in a single atomic operation, OR you have to explicilty lock.
