Archives of the TeradataForum
Message Posted: Thu, 04 Aug 2005 @ 19:35:42 GMT
| Subj: | | Re: Optimizer and Transitive Property of Equality |
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| From: | | Prescott, Kyle R |
If you are using v2r5.0 or above, you may want to contact your system administrator and verify your SATTC setting is invoked in the DBSCONTROL
parameters. The SATTC is the query Satisfiability and Transitive Closure. The transitive closure handles just what you are describing.
There has been a lot of work performed around this feature (and a few tech alerts). The optimizer will use hints from constraints (hard and
soft) when possible as well as transitive closure to optimize performance - you should see a=b,b=c, then a=c type logic in the explain.
Teradata's Horizontal and Vertical Partitioning concepts are driven using constraints as hints fed to the optimizer giving the optimizer the
chance to drop portions of a query that could not be satisfied due to the constraints on the data tables.
There are a couple of good explanations of this feature in the Teradata Partners Conference presentations called "Teradata Join Elimination"
and "Teradata Optimization".
Kyle Prescott
UnumProvident
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