Re: Is this a good definition for clustering factor

On Wed, 16 Feb 2005 18:18:35 -0700, Wolfgang Breitling <breitliw_at_centrexcc.com> wrote:
> Why invent another wheel? What is wrong with Oracle's definition?
> Oracle 9i (9.2) Database Reference:
> Indicates the amount of order of the rows in the table based on the values=
> =20
> of the index.
> - If the value is near the number of blocks, then the table is very well=20
> ordered. In this case, the index entries in a single leaf block tend to=20
> point to rows in the same data blocks.
> - If the value is near the number of rows, then the table is veryrandomly=20
> ordered. In this case, it is unlikely that index entries in the same leaf=20
> block point to rows in the same data blocks.

I like the tuning guide example. I don't like the descriptions above. In particular it seems to me that the first sentence is very poor english 'amount of order' is just an ugly phrase. I think that I would have used something like 'indicates how well the physical ordering of the rows in the table matches the order of the index'.

In addition both of the sentences " If the value is near the number of blocks, then the table is very well ordered." and especially "If the value is near the number of rows, then the table is very randomly ordered." would benefit from the addition of "by the keys of the selected index".The ordering of the table only makes sense in relation to the index being used to access it.  

-- 
Niall Litchfield
Oracle DBA
http://www.niall.litchfield.dial.pipex.com
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