:) I didn't study that stuff very much in my last five years at Oracle. Fast-full index scans weren't around when I was digging in the dirt. Anyway, things change across versions, and it's impossible to remember everything in one brain anyway...
So,... test! Cary Millsap Hotsos Enterprises, Ltd. http://www.hotsos.com Upcoming events: - Performance Diagnosis 101: 10/28 Phoenix, 11/19 Sydney - SQL Optimization 101: 12/8-12 Dallas - Hotsos Symposium 2004: March 7-10 Dallas - Visit www.hotsos.com for schedule details... -----Original Message----- [EMAIL PROTECTED] Sent: Friday, October 24, 2003 12:30 PM To: Multiple recipients of list ORACLE-L analytic function? you worked for oracle for 10 years and you have to guess? how secret do they keep these internals documents on the algorithms? > > From: "Cary Millsap" <[EMAIL PROTECTED]> > Date: 2003/10/24 Fri PM 01:19:25 EDT > To: Multiple recipients of list ORACLE-L <[EMAIL PROTECTED]> > Subject: RE: index full scan over an index fast full scan in an analytic function? > > The FF index scan reads all the block in the index, using multiblock > reads. The kernel then discards the branch blocks. If sorting of the > result set is required, then this is a separate row source operation, > because the rows don't come out of the segment in sorted order. > > To see why, imagine the following index "picture", which I'll draw > sideways, using indentation to denote the parent-child relationship. > It's a pretty stupid-looking index (Oracle can have many more children > per branch block than I'll draw), but it'll work to illustrate. I'll > label each block in the index with file#:block#. > > 23:14 > 23:15 > 23:18 > 23:19 > 23:22 > 23:20 > 23:17 > 23:25 > 23:24 > 23:21 > 23:16 > 23:23 > > To range-scan the rows in the index, the kernel would read the following > blocks from file 23 using 'db file sequential read', in this order: > > 18, 19, 22, 17, 25, 21, 16, 23. > > To FF scan the index, Oracle would read the following blocks using 'db > file scattered read' (assume a value of 8 for my example), in this > order: > > 14-21, 22-25 > > In using the results, the kernel would discard blocks 14, 15, 20, and > 24. As I said, if the kernel needed the rows in the remaining blocks to > be in logical order (as opposed to the physical order in which they were > obtained), then the kernel would have to sort them. > > This is how I think FF scan works. To be sure, trace a simple FF scan, > using extended SQL trace (event 10046 level 8). > > > Cary Millsap > Hotsos Enterprises, Ltd. > http://www.hotsos.com > > Upcoming events: > - Performance Diagnosis 101: 10/28 Phoenix, 11/19 Sydney > - SQL Optimization 101: 12/8-12 Dallas > - Hotsos Symposium 2004: March 7-10 Dallas > - Visit www.hotsos.com for schedule details... > > > -----Original Message----- > Mladen Gogala > Sent: Thursday, October 23, 2003 10:34 PM > To: Multiple recipients of list ORACLE-L > function? > > B*tree indexes are ALWAY ordered. That's the way they're created and > searched. > I don't know the difference between full index scan and fast full index > scan. > I know that the latter is used when the tble rows are not needed. Sounds > like > both methods are reading all leaf blocks, from start to finish, using > multiblock read. I am not aware of any difference between the two > methods. > This sounds like a question for asktom or ixora (Tom Kyte or Steve > Adams). > Wolfgang Breitling and J. Lewis might also know. > > On 2003.10.23 23:14, Larry Elkins wrote: > > Because when doing an index range scan things are read ordered? Very > > different from an index fast full scan where blocks are simply grabbed > where > > they might lie? > > > > Regards, > > > > Larry G. Elkins > > The Elkins Organization Inc. > > [EMAIL PROTECTED] > > 214.954.1781 > > > > > -----Original Message----- > > > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf > Of > > > Ryan > > > Sent: Thursday, October 23, 2003 9:34 PM > > > To: Multiple recipients of list ORACLE-L > > > Subject: Re: index full scan over an index fast full scan in an > analytic > > > function? > > > > > > > > > why would you not need a sort with a full index scan and need one > with a > > > fast full scan? > > > ----- Original Message ----- > > > To: "Multiple recipients of list ORACLE-L" <[EMAIL PROTECTED]> > > > Sent: Thursday, October 23, 2003 5:19 PM > > > function? > > > > > > > > > > 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). > > > > > > -- > > > Please see the official ORACLE-L FAQ: http://www.orafaq.net > > > -- > > > Author: Ryan > > > 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). > > > > -- > Mladen Gogala > Oracle DBA > -- > Please see the official ORACLE-L FAQ: http://www.orafaq.net > -- > Author: Mladen Gogala > 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: Cary Millsap > 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: Cary Millsap 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).
