The query which runs in 1 minute in oracle 8 takes hours in oracle 10.

Question

I have a query which takes longer time in oracle 10. I have looked at the parameters and it all seems to be right. I dont know what other parameter has to be changed in order to make it work. The strange thing is that if I addr another criteriain the where clause then the sql runs in less than one minute. I added AND J.DEPTID Between '00000' and '99999' in the where class which is not really required as without that also the query returns data for all depts as the dept number falls between 00000 and 99999. Following is the sql which takes long time to run.
SELECT
L.HRS_ADJUST_UNPROC,L.HRS_ADJUST_YTD,L.HRS_CARRYOVER,J.DEPTID,L.COMPANY, L.EMPLID, J.HOURLY_RT, P.NAME
FROM
PS_LEAVE_ACCRUAL L, PS_JOB J, PS_LOCATION_TBL LOC, PS_PERSONAL_DATA P
WHERE
(((L.PLAN_TYPE = '50') AND
(L.ACCRUAL_PROC_DT = (SELECT MAX(L2.ACCRUAL_PROC_DT)
FROM PS_LEAVE_ACCRUAL L2
WHERE L2.EMPLID=L.EMPLID
AND L2.EMPL_RCD_NBR=L.EMPL_RCD_NBR
AND L2.PLAN_TYPE=L.PLAN_TYPE)) AND
(J.EMPL_STATUS IN( 'A', 'L', 'P')) AND
((L.HRS_ADJUST_UNPROC+L.HRS_ADJUST_YTD+L.HRS_CARRYOVER+L.HRS_EARNED_YTD-L.HRS_TAKEN_UNPROC-L.HRS_TAKEN_YTD) <> 0) AND
(L.COMPANY = 'LHS') AND
((J.EFFSEQ= (SELECT MAX(INNERALIAS.EFFSEQ)
FROM PS_JOB INNERALIAS
WHERE INNERALIAS.EMPL_RCD_NBR = J.EMPL_RCD_NBR
AND INNERALIAS.EMPLID = J.EMPLID
AND INNERALIAS.EFFDT = J.EFFDT)
AND
J.EFFDT = (SELECT MAX(INNERALIAS.EFFDT)
FROM PS_JOB INNERALIAS
WHERE INNERALIAS.EMPL_RCD_NBR = J.EMPL_RCD_NBR
AND INNERALIAS.EMPLID = J.EMPLID
AND INNERALIAS.EFFDT <= SYSDATE))) AND
((LOC.EFFDT = (
SELECT MAX(INNERALIAS.EFFDT)
FROM PS_LOCATION_TBL INNERALIAS
WHERE INNERALIAS.LOCATION = LOC.LOCATION
AND INNERALIAS.EFFDT <= SYSDATE)))))
AND
(L.EMPL_RCD_NBR = J.EMPL_RCD_NBR ) AND (L.EMPLID = J.EMPLID ) AND (J.REPORTING_LOCATION = LOC.LOCATION ) AND (L.EMPLID = P.EMPLID )
ORDER BY
J.DEPTID, P.NAME

Answer 1

In fact I had tried with /*+RULE*/ hint and the query ran in 1 minute just like in Oracle 8 though the explain plan was almost same as without hintSounds like you are close to finding out what is happening differently and why it makes such a big difference. I think that was the point of Pete's suggestion, not to hope that the RULE hint would be a solution in itself. I sometimes try increasing the dynamic sampling level for the same reason.
btw please post code and execution plans in tags (see FAQ for details).
Also you can post the {noformat}<{noformat}> operator by placing {noformat} tags around the opening "<" symbol.
Edited by: William Robertson on Sep 9, 2009 10:41 PM