Bind variables and function based index

Hi List,
In continuation with my earlier post
This is the query. Couple of things I noticed about this is that this query does not use the Function based index created on suggested_vendor_name and also the explain plan repeats itslef (it does the same steps twice). Attached is the explain plan so that you see what I mean.

On the other hand if I replace these bind variables with actual values, it does use the index and no repeatition (in explain plan)

SELECT
  RH.SEGMENT1 REQUISITION_NUMBER,
  XXDL_REQ_WEB_INQUIRY.DECODE_PERSON_NAME(RH.PREPARER_ID) ORIGINATOR_NAME,   RL.SUGGESTED_VENDOR_NAME, RH.CREATION_DATE, RH.AUTHORIZATION_STATUS,   DECODE(NVL(PH.PO_HEADER_ID,'1'),'1',' ',NVL(PH.AUTHORIZATION_STATUS,   'INCOMPLETE')) PO_STATUS
FROM
 PO.PO_REQUISITION_LINES_ALL RL, PO.PO_REQUISITION_HEADERS_ALL RH,   PO.PO_REQ_DISTRIBUTIONS_ALL RD, PO.PO_DISTRIBUTIONS_ALL PD,   PO.PO_HEADERS_ALL PH, MTL_CATEGORIES MC WHERE 1=1 AND   UPPER(RL.SUGGESTED_VENDOR_NAME) LIKE UPPER(:B7 || '%') AND   RH.REQUISITION_HEADER_ID = RL.REQUISITION_HEADER_ID+0 AND

  RL.REQUISITION_LINE_ID = RD.REQUISITION_LINE_ID AND RD.DISTRIBUTION_ID =
  PD.REQ_DISTRIBUTION_ID(+) AND RD.EXPENDITURE_TYPE = NVL(:B6 ,
  RD.EXPENDITURE_TYPE) AND PD.PO_HEADER_ID = PH.PO_HEADER_ID(+) AND
  RH.CREATION_DATE BETWEEN :B5 AND :B4 AND RH.AUTHORIZATION_STATUS=DECODE(:B3

  ,'1',RH.AUTHORIZATION_STATUS,:B3 ) AND RL.CATEGORY_ID = MC.CATEGORY_ID AND   MC.SEGMENT1||'' = NVL(:B2 ,MC.SEGMENT1) AND MC.SEGMENT2||'' = NVL(:B1 ,   MC.SEGMENT2) AND ((MC.ATTRIBUTE9 = 'Y') OR (RH.PREPARER_ID =   FND_GLOBAL.EMPLOYEE_ID) OR
  (XXDL_REQ_WEB_INQUIRY.ISAPPROVER(RH.REQUISITION_HEADER_ID,   FND_GLOBAL.EMPLOYEE_ID) = 'Y')) ORDER BY RH.CREATION_DATE DESC  On Tue, May 6, 2008 at 5:56 PM, Mark Brinsmead <pythianbrinsmead_at_gmail.com> wrote:

> Using bind variables rather than literals can alter the cardinality
> estimates used by the CBO, and that can alter the execution plan.
>
> It might be helpful to provide the actual query, or at least the execution
> plans.
>
>
>
> On Tue, May 6, 2008 at 5:54 PM, Kumar Madduri <ksmadduri_at_gmail.com> wrote:
>
> > Hi
> > Is there any restriction with bind variables and function based indexes.
> > I noticed that if I have literals fbi is being used but if I replace that
> > with bind variables then fbi is not used. DB version is 10.2.0.1. You
> > cant seem to force it to use FBI through hints also. As I am investigating
> > this, I thought of posting here to see if there are any known issues or
> > restrictions that prevent function based indexes usage with bind variables.
> > QUERY_REWRITE_INTEGRITY is set to trusted and query_rewrite_enabled is
> > true.
> >
> > thank you
> > - kumar
> >
>
>
>
> --
> Cheers,
> -- Mark Brinsmead
> Senior DBA,
> The Pythian Group
> http://www.pythian.com/blogs

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text/plain attachment: bad_explain.txt



text/plain attachment: good_explain.txt