Re: Index Usage ?!

Once again thanx a lot Tanel for spending your precious time to make me understand.

Regards,
Jp.

28-07-2003 22:59:25, "Tanel Poder" <tanel.poder.003_at_mail.ee> wrote:

>The point is, that index access is cheap in reality, but CBO thinks it's
>very expensive and chooses next best executin plan in it's opinion, but this
>opinion is actually wrong, because unset optimizer_ parameters for example.
>One more thing, your test query returned no rows, it could be that with
>index access Oracle didn't even have to visit any table blocks because no
>relevant keys found in index. But when you'll have keys matching your query
>conditions in future, index access might get slower as well (here's where
>clustering_factor comes into play).

>Without analyzing, the index cost in reality is still low, and with
>super-optimistic default statistics CBO luckily picks that path.
>
>No, according plan in your orignal post, index range scan was used.
>Btw, I submitted a simple research about CBO table/index access costs to
>comp.databases.oracle.server yesterday under subject "2 Oracel doubts", you
>might want to read that one as well to get more understanding on your issue.
>
>Tanel.

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