Re: Performance / Index

From: <yitbsal_at_statcan.ca>
Date: 2000/04/13
Message-ID: <8d58pd$5vg$1@nnrp1.deja.com>#1/1

In article <38F353AD.3F4C9E5_at_solsuni.pt>, Duarte Nuno Sousa <Duarte.Sousa_at_solsuni.pt> wrote:
> Hi
> I'm having some performance problems with my index's.
> I have bitmap indexes and when i rebuild them, all the same queries
that
> before the rebuild takes about 1/2 minutes to run now it's running in
> 7/8 minutes.
> My Database have 120Gb and it's running in a Sun E3500 with 4
> UltrasparcII and have 2Gb of memory
> All the tips and Hits are Welcome.
>
> Duarte Nuno de Sousa
> duarte.sousa_at_solsuni.pt
>

How often is the column on which the bitmap index is based updated? I've found that a bitmap index quickly deteriorates if the column it is based on is updated often. Of course, bitmaps indexes should not be used on columns with high cardinality. Changing the cardinality, that is, if new values are introduced to the bitmap index, or existing values are deleted, then the performance deteriorates, too.

Salaam Yitbarek

Sent via Deja.com http://www.deja.com/
Before you buy. Received on Thu Apr 13 2000 - 00:00:00 CDT