RE: Maximum height of an Oracle B-tree index
- From: "Lex de Haan" <lex.de.haan@xxxxxxxxxxxxxx>
- To: <oracle-l@xxxxxxxxxxxxx>
- Date: Sat, 27 Mar 2004 14:59:48 +0100
I should have looked in my own documentation, of course -- thanks for the
correction Jonathan...
kdxcolev is indeed part of each branch or leaf index block, and it is UB1. I
also found the same note, saying that the max value is 23, so we have max 24
levels (0 thru 23) but unfortunately, I don't have an explanation why :-(
-----Original Message-----
From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx]On
Behalf Of Jonathan Lewis
Sent: zaterdag 27 maart 2004 14:18
To: oracle-l@xxxxxxxxxxxxx
Subject: Re: Maximum height of an Oracle B-tree index
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@xxxxxxxxxxxxxx>
To: <oracle-l@xxxxxxxxxxxxx>
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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