Metalink note 1011840.102 describes this. Tanel. P.S. I spelled algorithm wrong in my last post, now I'm a bit wiser again ;)
----- Original Message ----- To: <[EMAIL PROTECTED]> Sent: Monday, September 08, 2003 6:13 PM > Tim, > > AFAIK, when doing a rebuild the whole index is read using fast full scan, > the branch blocks are just ignored. And sorting does occur, since fast full > scan doesn't guarantee all keys to be returned in an order. (yes the keys > come in ordered "chunks" because they are stored in ordered way inside leaf > blocks, that might help the ordering alghoritm to complete faster). > > The benefit comes from that indexes are usually smaller in size than tables > because they index only subset of a row, thus there are less IO operations > needed when scanning data. > > Tanel. > > ----- Original Message ----- > From: "Tim Gorman" <[EMAIL PROTECTED]> > To: "Multiple recipients of list ORACLE-L" <[EMAIL PROTECTED]> > Sent: Monday, September 08, 2003 4:49 PM > Subject: Re: How to speed up index creation > > > Gunnar, > > Using ALTER SESSION to increase SORT_AREA_SIZE to some obscene number (i.e. > several hundred Mb? A Gb?) may help, as long as you are running 8i or below > or (if running 9i) the parameter WORKAREA_SIZE_POLICY is set to MANUAL. If > WORKAREA_SIZE_POLICY is set to AUTO, then you may have to bump > PGA_AGGREGATE_TARGET to something enormous instead... > > Are you making use of ALTER INDEX REBUILD to rebuild an index, or are you > dropping and then creating? ALTER INDEX REBUILD runs much faster than a > CREATE INDEX for two reasons: 1) the REBUILD reads the previous index�s > leaf nodes so there is less I/O since it is smaller and 2) there is no sort > operation needed since the previous index�s leaf entries are already sorted= > -- Please see the official ORACLE-L FAQ: http://www.orafaq.net -- Author: Tanel Poder 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).
