Hi Everyone,

I've got a JPA+Hibernate app that I'm trying to figure out what exactly the merge function does in EntityManager. In looking closely at our MySQL logs it would appear the merge generates a query which overwrites the state of the entire object to the database. What I would expect to happen though is that the merge compares each field/property of the entity and only overwrites the pieces that have truly changed.

For instance if I have a Dog entity with properties color and species and I change the color property and call merge the resulting query should be instead of the as i'm seeing.

Am I misunderstanding what the merge function is doing or its purpose? Is there some setting or setup that I am missing to make sure MySQL is getting more appropriate queries?

Thanks in advance,
Jean-Philippe

Is there really no one who can answer my question? I find this a bit hard to believe. Surely the devs who wrote the implementation would know.

Maybe my question is too confusing. Ok i'll try again. How can I get the EntityManager.merge() function to produce true merge SQL statements where only the field values that have actually been modified are set?