Oracle FAQ Your Portal to the Oracle Knowledge Grid

Home -> Community -> Mailing Lists -> Oracle-L -> RE: online index rebuilds - FFS or FTS

RE: online index rebuilds - FFS or FTS

From: Bobak, Mark <>
Date: Mon, 30 Jan 2006 16:39:14 -0500
Message-ID: <>

 No, not at all. "INDEX FULL SCAN" reads the index, starting at the root, one block at a time, and walks the tree, in index sorted order. "INDEX FAST FULL SCAN" is the equivalent of a FULL TABLE SCAN, but for an index. It reads using multiblock reads, results are NOT returned sorted, and the reading process simply "throws away" the content of the root and branch blocks.


Mark J. Bobak
Senior Oracle Architect
ProQuest Information & Learning

"There are 10 types of people in the world: Those who understand binary, and those who don't."

-----Original Message-----

From: Roger Xu [] Sent: Monday, January 30, 2006 4:20 PM
To: Jonathan Lewis;;; Bobak, Mark; ORACLE-L Subject: RE: online index rebuilds - FFS or FTS

I thought "fast full index scan" was just another name for "index full scan"?

-----Original Message-----

From: Jonathan Lewis [] Sent: Monday, January 30, 2006 2:06 PM
To:; Roger Xu;; Bobak, Mark; ORACLE-L Subject: Re: online index rebuilds

You can actually get an index full scan
(rather than fast full scan) for an offline index rebuild - and I thnk I decided the choice was cost-based even back in 8i.


Jonathan Lewis The Co-operative Oracle Users' FAQ Cost Based Oracle: Fundamentals Public Appearances - schedule updated 10th Jan 2006


Thinking about why full table scan is required for online index rebuild... Maybe the potential index block splits are the reason why index FFS can't be used for online index rebuild? Consistent reads should overcome this issue though, but maybe there is something we don't know...

Btw, with offline index rebuild the decision whether to go with FTS or index FFS is also cost based (at least 10.2). If I have only single-column table indexed then the offline rebuild may do an FTS instead of fasf full index scan. (also, even in the case of fast full index scan, rows have to be sorted anyway, because index fast full scan doesn't guarantee an ordered result).


For technical support please email or you can call (972)721-8257.
This email has been scanned for all viruses by the MessageLabs Email Security System.

This e-mail is intended solely for the person or entity to which it is addressed and may contain confidential and/or privileged information. Any review, dissemination, copying, printing or other use of this e-mail by persons or entities other than the addressee is prohibited. If you have received this e-mail in error, please contact the sender immediately and delete the material.

This email has been scanned for all viruses by the MessageLabs Email Security System. Any questions please call 972-721-8257 or email your request to

-- Received on Mon Jan 30 2006 - 15:39:14 CST

Original text of this message