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Message Posted: Thu, 08 Oct 2009 @ 09:47:49 GMT


     
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Subj:   Re: Cache for Optimizer
 
From:   Srihari Duddukuru

Hi There,

  Does Teradata Optimizer maintain it's own memory and stores query plan in it. In case same query is submitted again, does it goes thru entire process of syntax check, security check, etc. all over again?  


Teradata parser has the following sections:

1. Syntaxer 2. Resolver 3. Security 4. Optimizer 5. Generator 6. GNC Apply


Any query that has been submitted (the first time) has to go through all the sections of parser to come up with actual execution steps and these exec steps will be stored in software cache. The retention of these exec steps will be few hours (as per dbc control register)...

Later when the same query is executed, the request directly passes to GNC apply skipping all the steps except security check.

Note: The query that is being submitted the second time should be exactly same and any extra space between keywords also make the TD to consider that as a different query and parses the query completely


-Hari



     
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