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Message Posted: Wed, 01 Feb 2006 @ 18:10:03 GMT

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Subj:   Re: Use of Multiset for Large Table
From:   Dieter Noeth

Victor Sokovin wrote:

  Sure; but UPI might be considered in the following situation.  

  Suppose we have a large table in the end-user area of the DWH. It is SET and it has a performance problem with ETL processes. We change it to MULTISET but still do not want to have duplicate rows there because having duplicate rows in the end-user area is probably not a good idea. Then UPI might potentially be considered. Unfortunately, it might be difficult to find a good candidate UPI if it was not meant to be in the data model.  


Just re-read Michael's post:

There's no need for a Dup Check, because the PI is already unique and if some columns are unique then all columns must be unique, too :-)

  So, the point made is a few recent discussions is to have a multiset table but no duplicate rows in it (like in SET tables). My feeling is that it is often too difficult to achieve this on the database level so the responsibility should be delegated to ETL and QA processes.  

Full Ack.


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