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Message Posted: Thu, 27 Dec 2012 @ 20:05:53 GMT


     
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Subj:   Re: Maximum number of foreign key in a table in Teradata?
 
From:   frank.c.martinez

If you put on 32 secondaries, I can guarantee that the optimizer will never use some, and will probably never use most of them. I think if you ran a poll of the people on this list, you'd find not a lot of use of secondary indices. Somebody asked about Teradata architecture, and one of the aspects of that is, a secondary index won't be used if more than a certain amount of a particular table (is it 10% or 20%?) of the table is used. Because a full table scan is faster (think about that for a minute). And with PPI on a larger table, you can do a full scan of a small partition in a large table much quicklier.

iv

PS: And Dieter, you never weighed in on that skewing thing. You must have better distribution queries than me. Ok, than I.



     
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