I am using Hibernate 2.1 with ORACLE 8.

In a Hibernate Transaction if I am certain than instances of a particular entity class would be read but never updated, are there any optimizations I can do to hint Hibernate not to bother synching those instances to DB?

In a popular commerical ORM tool I had used, Unit-Of-Work makes available copies of entity instances and the object graphs are 'merged' at commit-time. In that case, there was a provision for the user to specifiy that an entity is never updated within a transaction, so that the tool can ignore merging of instances of that entity.

I am aware that Hibernate maintains a first-level cache that preserves object identity within a Session; so probably such an 'optimization' might not be making sense. Nonetheless, I am curious - can someone more experienced confirm?

Use session.evict(), session.clear(), or HQL projection queries.

It's ok, you can say the word "TopLink" here :-)

I havent forgotten the dirt the Cocobase guy kicked up ;)

Christian, your seem to suggest that at commit-time Hibernate will have to verify if an entity in first-level cache is "dirty" or not; and hence evicting the entity from the cache will prevent this check. Did I understand you correctly? Please let me know.

Yes, as documented.

Keeping tracking of all instances of a particular class is bit bothersome for me.
If there were a way to get all instances of a particular class from the (first-level-cache of) Session I could have used that, but I could not find such an API.

Is there any neater way to have the effect of read-only-entities without resorting to keeping tracking of all instances manually?

Use projection queries in HQL, ie. a select clause that returns more than one "column".

Hi Chrstian,

Thanks for replying.

The usecase I have in mind is slightly different and can't use projection queries. I load an object graph into memory, perform some operations/modifications on them, and eventaully I commit the transaction. When I commit the transaction, as far as I understand, Hibernate checks if any instance in the object graph is dirty and updates the data in the DB.

While doing this, if I am certain that instances of a particular entity class wont change. I am looking for some API where I can hint Hibernate not to bother checking dirtiness of some portion of the object graph. I expect this to be slightly more performant than the regular way.

I cannot use projection queries here because I dont want the whole object graph to be non-transactional.

I was expecting something like :

Kindly advise how to handle such cases.

Thanks again for your time.

Uhm, you could try mutable='false' on the class mapping (or setting it on Configuration before building the SessionFactory). Still, I believe that evict() is probably the granularity you are looking for.