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Message Posted: Mon, 05 Apr 2010 @ 08:12:10 GMT


     
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Subj:   Re: Performance Tunning and Explain
 
From:   s.khurana

Also would like to add :

Diagnostic helpstats on for session is over generous and gives all possible combinations of stats which can be collected

Single column stats recommended can be collected but you need to give a second thought and testing before collecting Multi column stats recommended by this comman.

Also I have seen scenarios (for Tables involved in subquery in a big query) ..In which this command does not recommend any stats - even single column.

Best way is to go through Explain and look for steps in which Retreival from a single Table is there with low or no confidence.

Joins,aggregations,sorting etc may have low no confidence in the explains even you have collected stats .


Thanks-

Sachin Khurana



     
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