Possibly to avoid a sort operation (assuming that you might be able to get away with a NOSORT when doing the full index scan)? It might be deciding that the benefit of the multi-block reads for the fast full scan are more than offset by the sort operation that would be needed (and might not be needed when doing the full index scan).
Regards, Larry G. Elkins The Elkins Organization Inc. [EMAIL PROTECTED] 214.954.1781 > -----Original Message----- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of > [EMAIL PROTECTED] > Sent: Thursday, October 23, 2003 2:39 PM > To: Multiple recipients of list ORACLE-L > Subject: Re: index full scan over an index fast full scan in an analytic > function? > > > i cant attach the 10053 trace. it has proprietary info. There > isnt much in analytic explain plan either. > > does anyone know in general why a full scan would be faster than > a fast full scan? > > > > From: <[EMAIL PROTECTED]> > > Date: 2003/10/23 Thu PM 03:09:26 EDT > > To: Multiple recipients of list ORACLE-L <[EMAIL PROTECTED]> > > Subject: index full scan over an index fast full scan in an > analytic function? > > > > I have an index on the two columns used in this query. Why > would the optimizer choose an index full scan over an index fast > full scan? > > > > My question isnt why an index is used, but the type of index scan? > > > > select * > > from (select col1, col2, > > dense_rank() > > over (partition by col1 > > order by col2 desc)tab > > from mytable) > > where tab = 1 > > > > -- > > Please see the official ORACLE-L FAQ: http://www.orafaq.net > > -- > > Author: <[EMAIL PROTECTED] > > 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: <[EMAIL PROTECTED] > 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: Larry Elkins 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).
