Re: BITMAP Versus B-TREE
- From: "Jared Still" <jkstill@xxxxxxxxx>
- To: yoursraju007@xxxxxxxxx
- Date: Tue, 26 Jun 2007 12:28:25 -0700
On 6/25/07, Raj Mareddi <yoursraju007@xxxxxxxxx> wrote:
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...
You may want to consider how this index is used, or even if it is ever used at all. The CBO may be ignoring it entirely, or possibly even using it when it is not a good idea. What is the skew of these 2 values? To engage in a bit of hyperbole: If the skew is 99% NO, and there are never any quries with YES as a predicate, the index is just a drain on resources. -- Jared Still Certifiable Oracle DBA and Part Time Perl Evangelist