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Re: How are INDEXES BALANCED?

From: Dan Clamage <clamage_at_mime.dw.lucent.com>
Date: 1997/09/16
Message-ID: <01bcc2ab$3d46fd70$54110b87@clamagent>#1/1

> Ardley Tschetter <ardley_at_interaccess.com> wrote...
> > I need to know if an index is not balanced, how do I get it balanced or
 is
> > it done automatically? For example, when I enter an order number to an
> > order entry system and the numbers are sequentially numbered, are the
> > records added to the b-tree in one straight line to the tree?
>
> Dennis Taylor <no_spam_dammit_at_ipipeline.net> wrote...
> The short answer is that Oracle automatically balances an index (or so
 I've
> been told). The logic for doing so is straightforward enough that, if
 they
> didn't, you'd have to go over and slap Larry Ellison upside the head.
>

The long answer is contained in any good textbook on database systems design or data structures. The use of Balanced B+ Trees (using various well-documented algorithms) has been with us for over 10 years. Only freshman CS majors taking the requisite C programming class use plain vanilla B-trees.

Unlike some ancient systems like the IBM System/23 with its ISAM files, modern indexes are auto-balanced by the insertion/deletion algorithms used on balanced B+ trees, and do not need periodic reorganization. The only real maintenance indexes require is found in managing their extents.

Received on Tue Sep 16 1997 - 00:00:00 CDT

Original text of this message

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