Can I ask for the following: 1) The clustering factor on the index 2) number of distinct keys 3) number of leaf blocks
Dick Goulet Senior Oracle DBA Oracle Certified 8i DBA -----Original Message----- Sent: Wednesday, November 05, 2003 4:05 PM To: Multiple recipients of list ORACLE-L But that doesn't really explain why the optimizer chooses an FTS with a predicate that presumable is more selective (name like 'ABC%') and an index scan with a predicate that presumable is less selective (name like 'AB%'). I could understand it if it were the other way around. Is there a histogram on the name column? At 11:34 AM 11/5/2003, you wrote: >Sami, > > Your problem is not with the index, but rather the cost based > optimizer. Most of us have been beat severely over the head and > shoulders through the years that full table scans are a BAD thing, me > included BTW. Well, it's time for the old dog to learn new tricks. So > that I'm not a long winded person, take a look in Select magazine, 3rd > qtr 2003, for the article "In Defense of Full Table Scans" by Jeff > Maresh. For a long time the CBO was a mystery to me as well especially > when it did unexpected things like this. I've applied Jeff's ideas on > computing an index's efficiency to see if it explained what the CBO > did. Amazingly in 95% of the cases I've analyzed it made absolute sense. > > I'm including Jeff with a courtesy copy of this message so that > 1) I can pat him for making the waters clear and 2) so he can add > anything he desires. > >Dick Goulet >Senior Oracle DBA >Oracle Certified 8i DBA Wolfgang Breitling Oracle7, 8, 8i, 9i OCP DBA Centrex Consulting Corporation http://www.centrexcc.com -- Please see the official ORACLE-L FAQ: http://www.orafaq.net -- Author: Wolfgang Breitling INET: [EMAIL PROTECTED] Fat City Network Services -- 858-538-5051 http://www.fatcity.com San Diego, California -- Mailing list and web hosting services --------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing). -- Please see the official ORACLE-L FAQ: http://www.orafaq.net -- Author: Goulet, Dick INET: [EMAIL PROTECTED] Fat City Network Services -- 858-538-5051 http://www.fatcity.com San Diego, California -- Mailing list and web hosting services --------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).