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

What were the logical reads query + current during this same test.  Physical reads could be
different because the first query loaded the rows into memory.

John

Michael.Johnson_at_oln-afmc.af.mil wrote:

>All the columns in the table are not null ...
>
>here is an interesting test I ran ...
>
>several Direct_Path_Write and Read waits with large elasped times
>are showing up in the 10046 trace data on this query due to the
>full table scan.
>
>Just deleted statistics on this and fwiw ...
>
>With Statistics ....
>=====================
>
>SELECT Statement Optimizer=Choose (Cost=225 ...)
> SORT (Order By) (Cost=225 ...)
> Table Access (Full) of 'table1'
>
>Physical Reads = 433
>
>Without Statistics ..
>======================
>
>SELECT Statement Optimizer=Choose
> Table Access (By Index Row) of 'table1
> Index ( Full Scan ) of 'concatenated index' (Non-Unique)
>
>Physical Reads = 0
>
>Mike
>
>-----Original Message-----
>Sent: Thursday, January 23, 2003 6:29 PM
>To: Multiple recipients of list ORACLE-L
>....
>
>
>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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