Re: Disadvantages of Bitmap Indexes?

From: Niall Litchfield <n-litchfield_at_audit-commission.gov.uk>
Date: Wed, 11 Oct 2000 13:14:30 +0100
Message-ID: <8s1lja$1g6$1@soap.pipex.net>

The disadvantage and the reason for the warning is that the bitmap index has to be recalculated in its entirety for each of those operations. I believe it also locks the underlying table while it does this , but I may well be wrong about that.

HTH

--
Niall Litchfield
Oracle DBA
Audit Commission UK
<joseharvey_at_my-deja.com> wrote in message
news:8s1g7p$ul8$1_at_nnrp1.deja.com...


> Hi gurus,

> I have a table containing about a million records. One column refers to

> an object type used as a foreign key to another table; there are about

> 150 different possible values. I think a bitmap index would be a good

> choice here; on our test environment it emproves performance

> dramatically. However, on my documentation there is a sentence about

> locking that makes me hesitate:

>

> "Bitmap indexes benefit data warehousing applications but they are not

> appropriate for OLTP applications with a heavy load of concurrent

> INSERTs, UPDATEs, and DELETEs."

>

> What is the meaning of "heavy load"? On my application, there will be

> about 1200 rows per week inserted on this table, performed by up to 150

> users. Will the bitmap index decrease performance considerably?

>

> Thanks for your answers

>

>

> Jose Harvey

>

>

> --

> -=[ Sancho ]=-

>

>

> Sent via Deja.com http://www.deja.com/

> Before you buy.

Received on Wed Oct 11 2000 - 07:14:30 CDT