Re: CBO not using the index even though it is faster when hinted ....

Johnson, Michael,

		Does use index really faster than using FTS? You are getting all the data from the table, and unless the sort is really that cost, I think full table scan is preferred. And the order of the data in the table(the clustering factor in index) is another important thing.
		IF you really want to use index and it is faster, try adjust :optimizer_index_caching, optimizer_index_cost_adj. Also try enlarge the sort_area_size and sort_area_retained_size, maybe this way, FTS will be faster?

Regards
zhu chao
msn:chao_ping_at_163.com
www.happyit.net
www.cnoug.org(China Oracle User Group)

• 2003-01-23 18:28:00 ,you wrote£º=======

>Anyone have any problems with the CBO not using
>a index when you know it is faster by forcing a
>hint ?
>
>I have set the following ...
>
>Solaris
>Oracle Version 8.1.7.4
>
>block size = 8
>DB_FILE_MULTIBLOCK_READ_COUNT = 8
>mode = Choose
>
>also using Tim Gormans 90 and 50 values for the other optimizer parms.
>
>Select col1, col2, col3, blah1, blah2 from table order by col1, col2, col3;
>
>
>Concatenate index on col1, col2, col3.
>
>
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>Author: Johnson, Michael
> INET: Michael.Johnson_at_oln-afmc.af.mil
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