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

I believe (pulling back my tuning memory which has been jump started of late) that
the order by is applied AFTER all the rows have been returned by the query. Thus,
your query is effectively this:

Select col1, col2, col3, blah1, blah2 from table;

Then the order by is applied. Since there is no predicate, no index is used, nor can
it be used. You might be able to use and index if you do something like this:

Select col1, col2, col3, blah1, blah2 from table where col1 >= min_val_col1 and col1 <= max_val_cols order by col1, col2, col3;

That should get you an index range scan. I think this will work. Someone please correct me if I'm wrong.

Robert

-----Original Message-----
Michael
Sent: Thursday, January 23, 2003 8:29 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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Author: Robert Freeman
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