What if I wanted to just read everything from the cache at once, with lazy instantiation set to false for all associations, then close the hibernate session. Would there be significant overhead in accessing the POJO classes and methods compared to just filling out POJO objects myself?

Thanks.

Depends if the Entity's associations contain alot of data. If you do not need the data then why load it? You can always "join" on the property you need within the HQL statement. Sometimes you feel like a nut sometimes you don't! Sometimes it is worth marking an association lazy=false because it does not incurr a performance hit and is used most of the time the parent is retrieved. Do your uses cases justify marking the association lazy=false?

The response time must be fast so it should be retrieved from a cached source. The data doesn't change much and is read more often so every hour or so, the cache is updated from the database, otherwise the cache is read most of the time.

In hibernate 2, when it was operating from the cache, I noticed some oddities like high CPU just reading the cache, not sure if this happens in v3.

Which begs another question, if I do an HQL query, can I make it use the cache to retrieve the item? And what is the lookup like, is there an in-memory hash of the objects where it maps from ID to the object instance, making lookups by ID fast? Is there a way to "add an index" to the cache so you can look up objects quickly by any property?

High CPU usage: Are you caching a lot of data? Meanning do you have enough memory to hold all the data you are caching? Sounds like a paging issue.


can I make it use the cache to retrieve the item:

Good question read 19.3. Managing the caches

And what is the lookup like, is there an in-memory hash of the objects where it maps from ID to the object instance, making lookups by ID fast?

Calling load or get is faster then executing an HQL statement. The difference between load and get is that load will throw an exception if the id is not found.

Is there a way to "add an index" to the cache so you can look up objects quickly by any property?

No, it only works of the id field.

thanks. I think I'll just make the database use a ramdrive for storage to allow me to do arbitrary queries in memory, using hibernate for POJO access.

Please read the cache chapter of the manual. You can cache pretty much anything, including query results.