Re: index rebuilding...

Jonathan Lewis wrote:

> Don,
>
> It's perfectly okay to say that the article that
> comes up is one of yours - after all, a user who
> is searching google in their local language may
> have something completely different as the
> second hit.
>
> A couple of points, by the way:
>
> Oracle B-tree indexes are balanced: every leaf
> is the same height from the root, it is not possible
> for some leaf blocks to have height three and others
> to have height four. (This is an error I used to make
> as well, before I sat down and though about block
> splits).
>
> The 'gets per key' is affected by the typical number
> of table rows per key - so rebuilding the index because
> it exceeds any particular level is unlikely to be of any
> benefit. The formula for this column is roughly:
> height + half of (rows in index / distinct keys in index)
>
> I can't think why the factor of a half has been included
> though.
>
> --
> Regards
>
> Jonathan Lewis
> http://www.jlcomp.demon.co.uk
>
> Coming soon a new one-day tutorial:
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> Don Burleson wrote in message
> <998d28f7.0301310721.3c724ec_at_posting.google.com>...
> >Hi,
> >
> >Do a Google search on "oracle index rebuild".
> >
> >The second hit has a good article on the topic.

I never thought I'd ever try to correct you but I believe (sticking it way out there on ths one) it is possible for there to be four on one and three on the other from time-to-time as Oracle doesn't rebalance every time someone performs a single insert or delete. Isn't it more a case of never having 5 and 3?

Daniel Morgan Received on Fri Jan 31 2003 - 11:04:20 CST