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Message-ID: <3F452387.3060300@gmx.ch>
Date: Thu, 21 Aug 2003 21:54:47 +0200
From: Jakob Braeuchi <jbraeuchi@gmx.ch>
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To: OJB Developers List <ojb-dev@db.apache.org>
Subject: Re: performance: surpress  m:n collection deletion on insert
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hi oli,

your patch got lost.

jakob

oliver.matz@ppi.de wrote:

>Hello,
>
>I have found and fixed a performance issue.
>
>Suppose you have a pc class A with a collection field
>with itemClass B, and supose that collection is mapped to an
>indirection table A_B.
>
>If you insert a fresh A instance with a null collection,
>then this results in one INSERT statement for the A 
>table and one DELETE statement for the indirection table A_B.
>
>The latter should usually be superflous, since there should
>not be any entries in the indirection table.  If there are
>ones, this is probably an error.
>
>In my proposed fix, I surpress the deleteMtoNImplementor() call
>inside storeCollections().  
>
>If you consider this change of behaviour risky, then I would
>like to propose to add a configuartion parameter that allows
>to force the old behaviour.
>
>In my model, the proposed fix results in a significant 
>performance improvement because the class A has severall
>collection fields which are mostly null.
>
>If you have another idea how to surpess the superflous calls,
>I would like to know.
>
>What do you think?
>
>Olli
>  
>
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