![]() ![]() The second one will commit a bit later, silently overwriting the data persisted by the previous one.One of them will commit earlier, persisting its changes to database.Both of them are making different changes.Both of them are reading the same state of the record.It solves dirty reads phenomena, which guarantees that the transaction reads only committed data by other transactions.īecause of the isolation level and of the concurrent nature of the transactions, the conflict could happen when two transactions have been processed simultaneously: In most RDBMS the default transaction isolation level is at least read committed. While concurrency avoidance is out of scope of this article, I will provide you some hints for the other 4 questions: Concurrent Database Transactions Problem What are the drawbacks of using pessimistic locking?.What problems does pessimistic locking solve?.Could you solve the concurrency problem with optimistic locking handling instead?.Could you avoid the concurrency for your concrete problem at all?.If you are interested on other pessimistic locking aspects please check direct the JPA and RDBMS provider's documentation.īefore you decide to embrace the pessimistic locking solution you should first have an answer to the following questions: □ Please note that this article is focused on exclusive row-level locks. the pessimistic locking could be the right choice! or if you need to implement some synchronization mechanism on database level like semaphores and so.If you expect to have many concurrent writers on the same row/-s in a relational database table.Moreover, I will give you some suggestions about when pessimistic locking might be the correct solution and when not.īut before that, let's take a closer look at what pessimistic locking is all about. In this article I will show you how you may overcome this limitation on Oracle, MySQL, PostgreSQL, Apache Derby and H2. ![]() Unfortunately its JPA support by different RDBMS providers is far from complete. One of the key properties for correct pessimistic locking handling and testing is LockTimeout. ![]()
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