Re: Rebuilding indexes

From: D.Y. <dyou98_at_aol.com>
Date: 4 Jun 2002 20:55:50 -0700
Message-ID: <f369a0eb.0206041955.1aef82e9@posting.google.com>

There are different ways Oracle can read an index. 1, follow the linked blocks and read the index in sorted order. Obviously

index keys read this way does not need to be resorted. But Oracle has to read one block at a time.
2, read everything in the allocated extents regardless how the blocks are

linked, so Oracle can read multiple blocks at a time. But index keys will need to be resorted.

I suspect Oracle might have used the latter approach, therefore the resort. But I have yet to test this myself.

"Chuck" <chuckhNOSPAM_at_softhome.net> wrote in message news:<adilc8$11hijm$1_at_ID-85580.news.dfncis.de>...
> I noticed fro mmonitoring v$sesstat that ALTER INDEX REBUILD does a sort
> operation. Why does Oracle need to resort the index keys if it's reading the
> source data from an existing index, and indexes are already sorted?
Received on Tue Jun 04 2002 - 22:55:50 CDT