Re: Tuning By cardinality Estimates
Date: Fri, 6 Mar 2009 10:31:24 -0600
You can read all about correlation in my blog below. BTW, 11g provides some relief with extended stats. Dynamic sampling at higher level also can provide some relief for columns with higher correlation.
But, do you have any index on (SRC, TF ,CDT)? That might make hash join plan cheaper and CBO might choose it.. Just a guess :-)
-- Cheers Riyaj Shamsudeen Principal DBA, Ora!nternals - http://www.orainternals.com Specialists in Performance, Recovery and EBS11i Blog: http://orainternals.wordpress.com On Fri, Mar 6, 2009 at 10:02 AM, Allen, Brandon <Brandon.Allen_at_oneneck.com>wrote:Received on Fri Mar 06 2009 - 10:31:24 CST
> A common example of correlated join criteria would be:
> select . . .
> where make='FORD'
> and model='MUSTANG';
> The CBO doesn't know that all Mustangs are built by Ford, so it's not aware
> that the extra filter condition won't really filter out any more rows.
> -----Original Message-----
> From: oracle-l-bounce_at_freelists.org [mailto:oracle-l-bounce_at_freelists.org]
> On Behalf Of hrishy
> I didnt quite understand the statement
> "Check if the join criteria between SC and SH are correlated"
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