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Home -> Community -> Mailing Lists -> Oracle-L -> OICA and Oracle choosing the wrong index
This is in reference to a new article by Jonathan Lewis about the OICA:
http://www.dbazine.com/jlewis18.shtml
It states that if you give Oracle a bad OICA it will choose the wrong index. Does anyone know why? I have run across this. I have cases where 95% of the time Oracle chooses the right index with a given OICA and for say 5% or less of queries Oracle chooses the wrong index.
I've noticed Oracle picking bad join orders depending on how I set there. Especially with joins of 3 tables or more.
Anyone have any comments or experiences? How much does CPU_COSTING eliminate this? We are still in development and have only delivered a small quantity of our application, so its not prudent to start messing with CPU_COSTING until I get a larger user sample.
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