Hi,

I'm new to Hibernate so I apologize in advance for any knowledge/vocab gaps.

I'm running a bunch of reports that require a rather large data set retrieved from the database. The first report retrieves ~500,000 items from the database, the next about 300k, the last about 300k. I'm setting all collections of objects to null immediately after use (prior to the next retrieval of data).

The first time I execute my Hibernate query, it takes about 40 sec; the next about 2-3 min, the following takes maybe 5 minutes, and then the last query (for the last report) takes a very long time, about 1-2 hrs. When I run this report by itself, it runs in about 5 minutes.

Does anyone know what the issue might be and how I can fix this?

Thank you in advance.

My first guess is that when you get to the third report there are lots and lots of already loaded entities in the first-level cache of the Hibernate Session object. Then, when you run the third report Hibernate will do it's automatic dirty-checking "magic" which can take a long time if the number of objects are large. There are a few possible solutions to this:

1. Use a new Session for each report
2. Call Session.clear() before each report to get rid of everything in the first-level cache
3. Call Session.setFlushMode(FlushMode.MANUAL) to avoid the automatic flushing and dirty-checking