But how does extended statistics solve the problem of join skewness by correlation? I believe that extended statistics in Oracle 11g is focused on the correlation of multiple columns of single table, not join correlation. ================================ Dion Cho - Oracle Performance Storyteller http://dioncho.wordpress.com (english) http://ukja.tistory.com (korean) ================================ On Sat, Mar 7, 2009 at 1:31 AM, Riyaj Shamsudeen <riyaj.shamsudeen@xxxxxxxxx > wrote: > Hrishys > > 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. > > > http://orainternals.wordpress.com/2008/03/21/correlation-between-column-predicates/ > > http://orainternals.wordpress.com/2008/12/19/correlation-nocorrelation-and-extended-stats/ > > 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@xxxxxxxxxxx > > wrote: > >> 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. >> >> Regards, >> Brandon >> >> -----Original Message----- >> From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx] >> On Behalf Of hrishy >> >> I didnt quite understand the statement >> "Check if the join criteria between SC and SH are correlated" >> >> >> Privileged/Confidential Information may be contained in this message or >> attachments hereto. Please advise immediately if you or your employer do not >> consent to Internet email for messages of this kind. Opinions, conclusions >> and other information in this message that do not relate to the official >> business of this company shall be understood as neither given nor endorsed >> by it. >> > > > >