Re: Reverse key Indexes Oracle 8.0

From: Robin Smith <smithrc_at_zdbaora.nat.bt.com>
Date: 29 Nov 1999 12:46:39 +0000
Message-ID: <x2ogcdbh3k.fsf@zdbaora.nat.bt.com>

cccccc_at_weee.co.uk (gw) writes:

> Can you please tell me when you would use the reverse key option on
> create index?
>
> What advantages does this give ?
> Any examples of use?
>
> The oracle 8 documentation is fairly sparse in this area.
>
> Thanks
> GW

Reverse key indexes are used to stop b*tree indexes "exploding" with a sequential dataload. If your first key of an index is a sequence then records will always be added to the right hand side of the index so it will become skewed. If you reverse the key then entries will also go into the middle of the index so will become self balancing.

e.g.

sequence	reverse
1000		0001
1001            1001
1002            2001

etc.

Robin Received on Mon Nov 29 1999 - 06:46:39 CST