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Message Posted: Wed, 07 Feb 2001 @ 17:30:24 GMT

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Subj:   Re: Collect Stat
From:   Donna Becker

To Dave's last point - Performance tuning analysis is the best way to determine whether statistics collection is needed. In some cases, queries using columns with no statistics can run the same or better as when there are statistics on those columns. My recommendation is first, collect on the Primary Index and any secondaries. Then second, just collect on columns in your WHERE clause that are weakly selective (columns with small domains). Then EXPLAIN some queries, and collect stats/add secondaries, etc. to "fix" the queries. By doing it this way, you won't collect on unnecessary columns, and you won't collect on columns that actually adversely affect the join paths.

Your mileage may very :-)

Just my two cents

Donna Becker
Senior Data Warehouse Consultant II
Teradata Division
Professional Services

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