yup.. over and over again. made sure it was compiled. Wierd thing is that I get a reduction in LIOs with the same plan if use an 'order by ' on the value in the index. really wierd. clustering factor should not be a factor in a 56 row table since all the index data should fit in one block. Its just 1 number field in the index. ----- Original Message ----- From: "Daniel Fink" <Daniel.Fink@xxxxxxx> To: <oracle-l@xxxxxxxxxxxxx> Sent: Thursday, August 12, 2004 3:41 PM Subject: Re: Really Wierd Query tuning issue > Ryan, > > Did you run the second query shortly after the first? What happens if you run the first query over and over? Are the logical I/Os of > the table/index or could they be related to parsing the statement? > > As for clustering factor, IIRC, that comes into play only when you are dealing with index range or full scans. For a unique scan, it > will return 1 index entry that points to 1 table row. For other scans, the CBO uses it to calculate how many table blocks will I > have to visit if I read a certain number of index entries. For example, a high clustering factor tells the CBO that the index > entries returned by the range scan (say 10% of the total) will require visiting a high number of table blocks (say 80%), so a full > table scan may be more efficient. > > Regards, > Daniel ---------------------------------------------------------------- Please see the official ORACLE-L FAQ: http://www.orafaq.com ---------------------------------------------------------------- To unsubscribe send email to: oracle-l-request@xxxxxxxxxxxxx put 'unsubscribe' in the subject line. -- Archives are at //www.freelists.org/archives/oracle-l/ FAQ is at //www.freelists.org/help/fom-serve/cache/1.html -----------------------------------------------------------------