Re: Suggestions please - Query loading 98%

Kenneth,

Perhaps the best (certainly the laziest) answer I can give in the forum is a pointer to an article I wrote recently for http://www.dbazine.com about how bitmap indexes are structured and how they work.

If you prefer it in Russian, it's also at:

    http://ln.com.ua/~openxs/articles/jlewis3_ru.html

--
Regards

Jonathan Lewis
http://www.jlcomp.demon.co.uk

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kennethkoenraadt_at_no-spam.hotmail.com wrote in message
<3da6874c.3453706_at_news.mobilixnet.dk>...


>Hi Jonathan,

>

>You are probably right all over the line. Especially the part about

>redesigning the application. The first thing I learned about tuning :

>"90% of performance gain comes from the application"

>apparently still seems to be true.

>

>I just have one question, that's your part about bitmap indexes :

>

>"Single row updates are likely (though not guaranteed)

>to make bitmap indexes explode if you are updating

>the indexed column"

>

>I noticed that the MSG_STATUS column is only updated within the

>existing range of values (WAITING,SUCCEEDED, FAILED). Updating the

>column from one of these values to another should only consist of

>changing a bitmap from '101' to '100' or so.

>

>I do not understand how that can make the index "explode" ?

>

> If new values of MSG_STATUS were introduced continously, I clearly

>understand the problem. But that is not the case here.

>

>

>- Kenneth Koenraadt

>