Index skip scan in my query plan?

Question

question

BI DWH BALA asked Dec 11, '09

I ran explain query plan for my query.

I found that in one step it is mentioned as "INDEX SKIP SCAN".

Does it mean the index is not used? Will it decrease query performance?

Any idea, why oracle is not using indexes?

Thanks, Regards,

BI DWH BALA

oracle performance index

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Answer 1 · 2009-12-11T16:14:03Z

Tariq Rahiman answered Dec 11, '09

Index skip scan is a performance feature
if you have a composite index on more than one column and you use the non-prefix column alone in your SQL, it may still use index with this feature
Index skip scan saves some disk space and overhead of maintaining another index

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BI DWH BALA commented · Dec 11, 2009 at 05:57 PM

This feature is really good one. Thanks for very good explanation.

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