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From Adam Hardy <>
Subject Performance with large lists
Date Fri, 11 Jun 2010 16:34:52 GMT
I have performance problems with large lists of beans due to the base 
class I am using for my entities.

This is slightly non-OpenJPA specific, so I hope nobody minds, but it is 
Friday afternoon so I'm hoping you give me a bit of slack here.

The problem arises when I start building lists with over 10,000 items on 
a parent class.

The trouble is in the base class for the entities, which is quite clever 
(but obviously not clever enough) and it has non-facile equals() and 
hashcode() algorithms which make use of reflection. It's here that the 
slow-down comes.

When I link the child with a parent that already has 10,000 children, 
the equals() method is called by ArrayList before the new child is 
placed in the index.

As far as I can tell I have a couple of options.

(1) ditch the reflection-based equals method and hard-code an equals method.

(2) don't use ArrayList but find a Collection-based class that uses 
hashes or similar to identify items instead of equals. This is just 
speculation - perhaps there is no such thing or it wouldn't help anyway:

     - would a collection using hashes caches the hashes of the items 
already indexed?
    - would such a collection be persistable?

If anyone has  been in this situation before, or has an idea about it , 
I'd really appreciate the help.


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