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Message Posted: Tue, 10 Apr 2012 @ 13:38:49 GMT

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Subj:   Re: Possible range of data skew
From:   Paddock, Eric

Theoretically? 0% on a UPI and 100% on a NUPI...

On a system with a UPI table containing 1 row per AMP with a PI value that (in some lucky happenstance) would send 1 row to a hash value on each amp (1 row per AMP) it would be 0%. The chance of this is small, though... Your skew with a UPI and > 1000 rows per AMP (a more real life scenario) should be < 1%... There are a couple oddities that cause more skewing on a UPI, but they are pretty rare...

And a NUPI could be 100% skew, if your table had all rows with the same PI value... This scenario happens to new Teradata implementers all the time...

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