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From: oliver.matz@ppi.de
To: ojb-dev@db.apache.org
Subject: RE: Identity.realClass and Identity.topLevelClass
Date: Fri, 29 Aug 2003 11:53:25 +0200
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Hej Thomas,

> -----Original Message-----
> From: Thomas Mahler [mailto:thma32@web.de]

> > I have had an idea how to improve the Identity class:

> > 2. lowestKnownClass - the lowest persistence-capable class
> >                    or interface (in the inheritance hierarchy)
> >                    that the identified object is known
> >                    to be an instance of.

> I agree that in your example (class C extends B extends A) it 
> will be a 
> performance improvement.
> 
> But will it be a performance improvement for arbitrary other 
> situations 
> (say class E extends D extends C extends B extends A) ?
> There could be some reference descriptors pointing to A, some others 
> pointing to B and even others pointing to C and D.
> How can the lowestKnownClass help in this case?

There will be no performance improvement for the reference
descriptors pointing to A, but there might be an improvement
for the others, depending on how many tables can be disregarded
in the search.  

Of course, this requires that the lowestKnownClass
is initialized correctly in each case, namely with the class
declared in the reference descriptor that it represents.

Olli

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