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From Jakob Braeuchi <jbraeu...@gmx.ch>
Subject Re: performance: surpress m:n collection deletion on insert
Date Thu, 21 Aug 2003 19:54:47 GMT
hi oli,

your patch got lost.


oliver.matz@ppi.de wrote:

>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?
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