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Message Posted: Wed, 23 Apr 2003 @ 16:19:35 GMT


     
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Subj:   Re: Join index successes?
 
From:   Claybourne Barrineau

At both my previous and current employer, we have had tremendous success using Join Indexes (both JI and AJI.) We have primarly implemented JIs as a solution to moving OLAP cubes back into the Teradata warehouse.

Main things to look out for:

1) Must have a thorough understanding of the tool generating the SQL which will use JIs inorder to limit cases where a JI is not a valid candidate

2) The more columns you incoporate into a JI, the less likely the optimizer is to use the JI because the JI may become 'too fat', and a full table scan of the JI might cost more than just joining the filtered underlying tables

3) If you have a case where you think a JI should be used by the optimizer, and it isn't, then open an incidient via Teradata's Global Incident Management web-site. The implementaiton of JI by Teradata customers is still in the early stages. Costing issues exist.

If you'd like, you can contact me off-line, and I will be happy to help.


Hope this helps,

Clay



     
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