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Re: Partitioning or BitMap-Index?

From: Ronald <devnull_at_ronr.nl>
Date: 13 Feb 2003 08:19:39 -0800
Message-ID: <67ce88e7.0302130819.3a76160@posting.google.com>


Christian Hartmann <cha_at_christian-hartmann.de> wrote in message news:<8kem4v0fge44up84noolhlajjl34pio1j1_at_4ax.com>...
> On Thu, 13 Feb 2003 03:38:16 +1100, "Howard J. Rogers"
> <howardjr2000_at_yahoo.com.au> wrote:
>
> >Is the column subject to change, ie DML? If so, run away from bitmap
> >indexes. A single bitmap index on a table is also not the world's most
> >useful thing -their power really comes from the combination of lots of
> >them.
> As I wrote in the other reply to the former posting I am currently
> using this column with possible values of 0 and 1. The data in this
> column is onyl created when the dataset is created in the table. There
> are no DML-Statements on this column and the column is used in every
> SQL-Statement witch run against the table in the where-clause.

Christian,

if the distribution of values is even I would not use an index on this column. I would if one value would have a very small number of rows compared to the other value and if the queries would select for the small group. The choice for bitmap or normal depends on the updates. You have no updates on this column so a bitmap could be usefull but only when there is a large differention in the number of rows. With an even distribution you might as wel have a full scan but you probably can use other columns to make a better index to minimize the scan with.

my vote is no index at all for this column, maybe add it to some other at the least significant side of the column list.

My 2 cents,
Ronald.



http://ronr.nl/unix-dba Received on Thu Feb 13 2003 - 10:19:39 CST

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