Start Hibernate executeupdate not updating

Hibernate executeupdate not updating

The SQL standard defines three consistency anomalies (phenomena): anomaly and that’s what we are going to discuss in this current article.

If there would be only one database transaction at any time then all operations would be executed sequentially.

The challenge comes when multiple transactions try to update the same database rows as we still have to ensure consistent data state transitions.

Choosing the isolation level is about finding the right balance of consistency and scalability for our current application requirements.

All the following examples are going to be run on Postgre SQL 9.3.

In this example Bob’s UPDATE must wait for Alice’s transaction to end (commit/rollback) in order to proceed further.

Read Committed accommodates more concurrent transactions than other stricter isolation levels, but less locking leads to better chances of losing updates.

Other database systems may behave differently according to their specific ACID implementation.

Postgre SQL uses both locks and MVCC (Multiversion Concurrency Control).

Follow @vlad_mihalcea A database is highly concurrent system.

There’s always a chance of update conflicts, like when two concurring transactions try to update the same record.

In MVCC read and write locks are not conflicting, so reading doesn’t block writing and writing doesn’t block reading either.