Question

So far, my preference has been to always use EntityManager’s merge() take care of both insert and update. But I have also noticed that merge performs an additional select queries before update/insert to ensure record does not already exists in the database.

Now that I am working on a project requiring extensive (bulk) inserts to the database. From a performance point of view does it make sense to use persist instead of merge in a scenario where I absolutely know that I am always creating a new instance of objects to be persisted?

Answer 1

It’s not a good idea using merge when a persist suffices – merge does quite a lot more of work. The topic has been discussed on StackOverflow before, and this article explains in detail the differences, with some nice flow diagrams to make things clear.