[Opensource] SEC: UNCLASSIFIED - RE: Urgent Help! Horrendous Expresso DBObject per formance problem.

[Michael Rimov]

At 08:35 AM 4/4/2003 +1000, you wrote:
>Thanks to all for this, I will try a custom cache, that should (hopefully :)
>get rid of the problem entirely.

I recommend the Maps:
EDU.oswego.dl.concurrent.ConcurrentReaderHashMap

or

org.apache.commons.collections.LRUMap

As the best data structures to consider.  LRUMap must have synchronized 
access, but removes 'stale unused' objects... on the flip side, 
ConcurrentReaderHashMap, you must manually remove stale objects, but you 
don't need to synchonize access (it's already done for you), and access to 
it is amazingly fast in comparison to synchronization.



>Out of curiosity, does anyone know what expresso is doing when retrieving a
>cached record that could be taking so long?

Like I mentioned in my previous email, my first guess would be the fact 
that when an object is retrieved from the cache, it is copied so different 
temp modifications don't corrupt the cache.  I've stressed the 5.0.3 
CacheManager fairly thoroughly and I don't believe that the performance hit 
would be in there, so if you could profile, I'd be checking 
DBObject.retrieveFromCache()

As folks know around here, I'm always interested in tweaking performance to 
higher levels, so if you find a good workaround, post it and we'll include 
it in future releases.

HTH,
                                                 -Mike