Re: Maximum height of an Oracle B-tree index

From: Jonathan Lewis <jonathan_at_jlcomp.demon.co.uk>
Date: Sat, 27 Mar 2004 13:18:09 -0000
Message-ID: <00b701c413fd$f4e74f70$7102a8c0@Primary>

The blevel has to be recorded in the block, and there is only one byte reserved for it, so there is a limit of 255 built in. However, Steve Adams suggested that the byte also can hold some unspecified flag information, so that reduces the maximum.

However, if only the low 5 bits were available for the blevel, I would have expected a maximum blevel of 31, height of 32, rather than Tanel's indication that the maximum height was 24.

Regards

Jonathan Lewis
http://www.jlcomp.demon.co.uk

The Co-operative Oracle Users' FAQ
http://www.jlcomp.demon.co.uk/faq/ind_faq.html

April 2004 Iceland http://www.index.is/oracleday.php June 2004 UK - Optimising Oracle Seminar

Original Message ----- From: "Lex de Haan" <lex.de.haan_at_naturaljoin.nl> To: <oracle-l_at_freelists.org> Sent: Saturday, March 27, 2004 12:05 PM Subject: RE: Maximum height of an Oracle B-tree index

: Jonathan,
:
: just thinking here -- I don't know of any internal reasons for a maximum
: B*-tree height in Oracle, right?
: any branch block only knows about its children, so we can go on splitting
as
: long as we like ...
:
: cheers,
: Lex.
:

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Received on Sat Mar 27 2004 - 07:14:46 CST