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Message Posted: Fri, 06 Sep 2002 @ 14:30:54 GMT


     
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Subj:   Re: Why all-amp macro?
 
From:   Frank O Connor

Hi

In the macro, you have asked the macro to do a full table scan. Teradata has to do a full scan of the table to get the data and it may not be always be sure that there is data on one amp (eg stale or no stats - teradata does not know if the stats are stale or not).

You will only get a single amp operation if you provide a distinct and single limit to a primary index value.

So if your macro has a predicate such as :

select *
FROM facdiscready
WHERE NUPI_CONST_F = 'a';

Then a single amp operation will occur.

Finally, you may need to consider your primary index choice. I assume from your question that your primary index contains a constant value. This means that the table relies on one amp and you are likely to suffer performance problems as you are not using the parallelism of Teradata.


God Luck

Frank



     
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