Our app was originally built with NHibernate and its limitations of batch processing in mind. However, over time it has transformed into a data cruncher and we are observing a significant performance decay.
The session ends up having to maintain about 1000 objects or more and our profiling has revealed that auto flushing and dirty checking are the biggest offenders here. We tried shutting auto flush and managing it ourselves on Save/Update operations but that led to disastrous performance for a batch save/update.
We’re now looking at the option of evicting unrequired objects from the session.
- I came across 2nd level-cache eviction method (
sessionFactory.Evict(typeof(Cat));) which lets us evict by type but we do not use a 2nd level cache. Can I still use this method to evict objects from the 1st level cache? - I also read about one pattern of fetching objects, evicting them from session, and then reassociating them, if needed, with session by calling Update() on them. Is this a recommended and accepted pattern cause I also read that NH3 has put up a wall to this? (We can still use it as we have not upgraded to NH3)
While we realize that we are not using NHibernate in the best way, we are just looking to improve the current situation somehow. Answers to the above questions and any other suggestions/recommendations are greatly appreciated. Thanks.
Update
After looking at NH documentation and code, I realize that 1 is probably not possible. I’m still looking at some pointers or tips on using Evict(). I was able to drastically reduce the number of objects in a session. But still do not know if there is a price to pay while updating or deleting evicted objects. Thanks for your help in advance.
It’s hard to say without knowing more about your requirements but maybe you could use IStatelessSession. It doesn’t have a 1st level cache to worry about.
Ayende has a good post on using it for bulk operations
here