Re: BITMAP Versus B-TREE

  • From: "Raj Mareddi" <yoursraju007@xxxxxxxxx>
  • To: RS2273@xxxxxxx
  • Date: Mon, 25 Jun 2007 16:01:46 -0400

Well, These indexes do exist already. For example, there is a column
called FLAG with values of 'YES' or 'NO' and there are 6 Millions of
rows in the index... but distinct values are only two ('YES' and
'NO')... Im just thinking to convert this to Bitmap... did couple of
ones and seen better performance... but just thining about loading on
these tables...

Thanks!



On 6/25/07, Shamsudeen, Riyaj <RS2273@xxxxxxx> wrote:
Raj
        If there is high DML activity on the table, then careful
consideration should be given while choosing bitmap index. By design,
bitmap indices are not suitable for tables with high DML activity.
        I have created bitmap indices on columns with very few distinct
values (10-) and also with high distinct values(Millions+), both
improving performance.
        But, you said there is just one distinct value for a column? Why
do you want to index that column?

Michael,

>>I find a little "buggier".
What do you mean "buggier"? Do you have specific test case that proves
that there are issues with bitmap index? And What version? What
administration overhead are you referring to ?

Thanks
Riyaj Shamsudeen


-----Original Message-----
From: oracle-l-bounce@xxxxxxxxxxxxx
[mailto:oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of Michael McMullen
Sent: Monday, June 25, 2007 8:16 AM
To: 'oracle-l'
Subject: RE: BITMAP Versus B-TREE

Do you mean the column has only one value, including nulls? I wouldn't
put
an index on that.
Yes, bitmaps are great for queries but a pain for loading. They can also
really favour certain access paths and I find a little "buggier". They
can
also grow like crazy.
I would say, if you heavily use bitmaps, it increases your
administration.
Like all things oracle, it's the details that kill you.


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