side effect of compound index

From: Anne Lendrow <alendrowny_nospam_at_msn.com>
Date: Thu, 20 Apr 2006 02:12:08 +0200
Message-ID: <e26jkp$bao$1@online.de>

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 Received on Wed Apr 19 2006 - 19:12:08 CDT