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

From: <Rajesh.Rao_at_jpmchase.com>
Date: Thu, 23 Jan 2003 19:53:50 -0800
Message-ID: <F001.00539352.20030123195350@fatcity.com>

How do you know an index scan would be faster? Did you get the query to use an index? What hint? Do you have the tracing stats for both with and without an index?
First, you dont have a where clause filter on an indexed column? If all the columns in the select were indexed, maybe u could have possibly used a Fast Full Index Scan hint?

Regards
Raj

                                                                                                                              
                    "Johnson, Michael "                                                                                       
                    <Michael.Johnson_at_oln-af        To:     Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com>        
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                    Sent by:                       Subject:     CBO not using the index even though it is faster when hinted  
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                    January 23, 2003 09:28                                                                                    
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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
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  INET: Rajesh.Rao_at_jpmchase.com

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Received on Thu Jan 23 2003 - 21:53:50 CST