In article <72pjd1$km5$1_at_nnrp1.dejanews.com>, slniemann_at_my-dejanews.com
writes
>I am trying to get some general information about bitmap indexes fitting to my
>situation.
>
>I have a database containing tables with rows of 750,000+
>
>In these tables is a foreign key of codes (72 distinct) which is set to its
>description table. These tables do receive a lot of update and insertion,
>many, many per day.
>
>As I understand it, the bitmap index works best with a static table, but
>would it be completely idiotic to form bitmap indexes for this column in
>these tables?
>
>I am still learning about bitmap indexes and could use any feedback you have.
>Thanks.
>
>
>S Niemann
>
>-----------== Posted via Deja News, The Discussion Network ==----------
>http://www.dejanews.com/ Search, Read, Discuss, or Start Your Own
Bitmap indexes are best for when there are very few different value
posibilities compared to the total number of rows. For example if you
have 10,000 rows and a column with 10/20 different possible values a
bitmap index would be useful.
We use bitmapped indexes on a number of tables in our data warehouse -
invoices, invoice lines, and the fact tables, none of which are static
in that they are being added to every day - although they are not being
amended or deleted from so do not match your situation.
The best thing I can suggest is 'suck it and see'! add a bitmap index,
measure performance, drop the bitmap and replace with a standard index
and measure performance.
Good luck.
--
Diane
Received on Tue Nov 17 1998 - 14:33:24 CST
