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Re: B-Tree index

From: Joel Garry <joel-garry_at_home.com>
Date: 6 Nov 2002 14:47:46 -0800
Message-ID: <91884734.0211061447.17ebd9b0@posting.google.com>


Brian Peasland <oracle_dba_at_peasland.com> wrote in message news:<3DC938AC.2058C850_at_peasland.com>...
> Your B-tree index will always be balanced. That's part of its
> definition! What you really want to check is to see if the leaf nodes
> are "empty". You can do this by issuing the following command:
>
> ANALYZE INDEX index_name VALIDATE STRUCTURE;
>
> Then query V$INDEX_STATS comparing the deleted leaf nodes to the total
> number. If this percentage is too high, then rebuild the index.
>
> HTH,
> Brian
>
> Harry Sheng wrote:
> >
> > How can I check if a B-Tree index (suppose it is not too big) is well
> > balanced ?

Check out the alter index coalesce command. (Some O8 Adminstrators Guides http://otn.oracle.com/docs/products/oracle8i/doc_library/817_doc/server.817/a76956/indexes.htm#4443 have a pretty picture illustrating what it does. If the illustration can be believed, the index is less balanced, although I think we have a semantics issue of "balanced." See also Note:76715.1 on metalink for an explanation.)

So my question is, if you're moving stuff around in the index like that, what is it called? It seems more than coalescing and less than defragmenting. Reverse-block-split-refreelisting? :-)

jg

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Received on Wed Nov 06 2002 - 16:47:46 CST

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