How does Oracle use indexes?
Date: Thu, 7 Oct 93 12:56:28 EST
Message-ID: <ds6i7300005_at_novalink.com>
Rick Writes...
A vendor has supplied an application with the following three indexes
on a table:-
Index1 uses columns col1, col2, col3, col4, col5, col6.
Index2 uses columns col1, col2, col3.
Index3 uses columns col1, col2.
I think index2 and index3 are redundant. The vendor says no.
Surely Oracle can use index1 in any situation when only some of those
leading columns are needed! Can anyone shed light on this problem?
Exact match index searches use a somewhat different strategy from range searches. It is concievable that you will get substantially better retrieval performance for some queries by having all three indexes. Clearly, you will incur more storage and update overhead. Try dropping one at at time and check your performance. Received on Thu Oct 07 1993 - 18:56:28 CET