Imagine that you have two objects, say Person and Event from the documentation. A person can have multiple event objects. Now imagine, that I have saved a person object which has twelve event objects associated with it.

If I make a change to the person object, but not to any of the events, and tell Hibernate to save the person object will it also make an update call for each of the twelve events?

If I make a change to the fourth event object in the person's list of twelve and then tell Hibernate to save the person will twelve update calls be made or just one?

If I retrieve the person object but never attempt to retrieve the person's events did any of the events get pulled from the database and placed into memory?

I'm curious how Hibernate deals with these sorts of optimization problems, any insight would be appreciated.

Thanks!

Hi,

First question: only Person will be saved,

Second question: only one Event will be saved,

Third question: it depends, with default configuration events won't be loaded unless they are necessary. This behaviour is controlled by 'lazy' attribute on collection. Read about 'lazy' loading in manual.

I recommend studying logs from Hibernate. It may be confusing at the very beginning, but later on it gives lots of information about what Hibernate is exactly doing. Personally I have found them very useful in understanding Hibernate.