Re: side effect of compound index

Anne Lendrow wrote:
> Hi,
>
> we are currently struggling with quite a slow SQL-Statement. When we use
> a Bitmap Index on 3 fields of the table, the SQL-Statement needs to
> finish its operation approximately 30 seconds.
> Now we changed the composite index to cover 4 fields and is not
> bitmapped. The SQL-Statement is now finished in < 1 second.
>
> In fact, the cardinality of the fourth, new field is high, the usage of
> a Bitmap Index wouldn't be a good idea, but maybe using this new
> composite index (4 fields instead of 3, where the cardinality of the 3
> fields of the old index is low) will have other side effects. Could you
> please help me to figure out these side-effects?
>
> Thanks for your help,
> Anne

Likely the only side effect will be better running queries.

Every time you make a change like this you should be running an EXPLAIN PLAN and documenting the effect.

-- 
Daniel A. Morgan
http://www.psoug.org
damorgan_at_x.washington.edu
(replace x with u to respond)