Re: optimizer not using function based indexes

you don't need the upper(ename) in your where clause... that forces oracle to NOT use an index

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|        |                             |
|        |                             |
|        |          Harvinder.Singh_at_met|
|        |          ratech.com         |
|        |                             |
|        |          05/09/2002 04:18 PM|
|        |          Please respond to  |
|        |          ORACLE-L           |
|        |                             |


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  >----------------------------------------------------|
  |                                                    |
  |       To:     ORACLE-L_at_fatcity.com                 |
  |       cc:     (bcc: Rachel Carmichael)             |
  |       Subject:     optimizer not using function    |
  |       based indexes                                |
  >----------------------------------------------------|

Hi,

We are trying to use function based indexes in our application but it looks like

optimizer is not using them.
So we created a sample table emp with 3 columns empno,ename,sal and populate this table with 100000 rows and created function based index on upper(ename). we try to run simple query like below and optimzer is not using index: select sal from emp
where upper(ename)=upper('abc98');

Even we use index hint optimizer is still not using index.....

1. table is analyzed as compute after creating index.
2. query rewrite is granted to user
3. query_rewrite_enabled=true.
4. optimzer mode is choose.
5. optimer should use index as there is no way full scan can be faster than index in this case as i tried to create simple index on ename and remove upper function from where clause of query..

What can be the possible reason that optimzer is not using index??????

Thanks
--Harvinder

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Author: Harvinder Singh
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  INET: Rachel_Carmichael_at_Sonymusic.com

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