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Re: When to use bitmap index based on cardinality

From: Martin Haltmayer <Martin_Haltmayer_at_KirchGruppe.de>
Date: Thu, 11 Feb 1999 08:19:22 +0100
Message-ID: <36C2847A.474EDC51@KirchGruppe.de>


How about updates/inserts/deletes? I was always told that bitmap indexes are weak here.

Martin Haltmayer

Christopher M. Day schrieb:
>
> Cutler,
>
> (A view from 8.0.5.11)
> I would agree, up until a couple of days ago ! Check out the
> proceedings from the OpenWorld'98 conference in SF on www.oracle.com.
> There was a presentation about using bitmaps on everything but UNIQUE
> columns.
>
> I tried this on two tables. One contains a unique key for all the
> households in the UK (hurn key) (b*tree), its child contains the hurn
> key and a person unique key. I used to have a b*tree on the child hurn
> column and have since changed it to a bitmap. The result was less
> storage and an increase in performance...
>
> Chris
>
> cutler_temp_at_usa.net wrote:
> >
> > I'm on Oracle 7.3.4.2
> >
> > The Oracle Tuning documentation says this about bitmap indexes:
> > <
> > Bitmap indexes can substantially improve performance of queries with the
> > following characteristics:
> >
> > The WHERE clause contains multiple predicates on low- or medium-cardinality
> > columns....
Received on Thu Feb 11 1999 - 01:19:22 CST

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