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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
>
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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