Re: Bitmap Indexes

From: <nelsona_at_my-dejanews.com>
Date: Wed, 19 Aug 1998 15:53:59 GMT
Message-ID: <6reseo$nf7$1@nnrp1.dejanews.com>

In article <mHvC1.2056$ds2.687553_at_news.tpnet.pl>, "Dariusz Trocha" <trocha_at_friko5.onet.pl> wrote:
> I'm afraid, optimizer won't take a bitmap index plan unless:
> - it can use two or more bitmap indexes simultaneously or
> - you put a hint forcing him to do this
>
> Darek
>
>

What a crock!!!

The optimizer WILL use a single bitmap index. I've witnessed it numerous times, and it works quite nicely.

Just make sure that your table has been analyzed after you have built your indexes using

analyze table ... compute statistics for table for all indexed columns

and analyze your indexes

analyze index .... compute statistics.

Keep in mind however, that if you have a bitmap index on a column that is frequently updated, you will pay a price in additional overhead to maintain the index.

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