SQL Query Performance needed.

Question

Hi All,
   I am getting performance issue with my below sql query. When I fired it, It is taking 823.438 seconds, but when I ran query in, it is taking 8.578 seconds, and query after in   is taking 7.579 seconds.
SELECT BAL.L_ID, BAL.L_TYPE, BAL.L_NAME, BAL.NATURAL_ACCOUNT,
 BAL.LOCATION, BAL.PRODUCT, BAL.INTERCOMPANY, BAL.FUTURE1, BAL.FUTURE2, BAL.CURRENCY, BAL.AMOUNT_PTD, BAL.AMOUNT_YTD, BAL.CREATION_DATE,
 BAL.CREATED_BY, BAL.LAST_UPDATE_DATE, BAL.LAST_UPDATED_BY, BAL.STATUS, BAL.ANET_STATUS, BAL.COG_STATUS, BAL.comb_id, BAL.MESSAGE,
 SEG.SEGMENT_DESCRIPTION  FROM ACC_SEGMENTS_V_TST SEG , ACC_BALANCE_STG BAL where BAL.NATURAL_ACCOUNT = SEG.SEGMENT_VALUE AND SEG.SEGMENT_COLUMN = 'SEGMENT99' AND BAL.ACCOUNTING_PERIOD = 'MAY-10' and BAL.comb_id
in  
(select comb_id from
 (select comb_id, rownum r from
  (select distinct(comb_id),LAST_UPDATE_DATE from ACC_BALANCE_STG where accounting_period='MAY-10' order by LAST_UPDATE_DATE )    
     where rownum <=100)  where r >0)
Please help me in fine tuning above. I am using Oracle 10g database. There are total of 8000 records. Let me know if any other info required.
Thanks in advance.

Answer 1

In recent versions of Oracle an EXISTS predicate should produce the same execution plan as the corresponding IN clause.
Follow the advice in the tuning threads as suggested by SomeoneElse.
It looks to me like you could avoid the double pass on ACC_BALANCE_STG by using an analytical function like ROW_NUMBER() and then joining to ACC_SEGMENTS_V_TST SEG, maybe using subquery refactoring to make it look nicer.
e.g. something like (untested)
WITH subq_bal as
    ((SELECT *
      FROM (SELECT BAL.L_ID, BAL.L_TYPE, BAL.L_NAME, BAL.NATURAL_ACCOUNT,
             BAL.LOCATION, BAL.PRODUCT, BAL.INTERCOMPANY, BAL.FUTURE1, BAL.FUTURE2,
             BAL.CURRENCY, BAL.AMOUNT_PTD, BAL.AMOUNT_YTD, BAL.CREATION_DATE,
             BAL.CREATED_BY, BAL.LAST_UPDATE_DATE, BAL.LAST_UPDATED_BY, BAL.STATUS, BAL.ANET_STATUS,
             BAL.COG_STATUS, BAL.comb_id, BAL.MESSAGE,
             ROW_NUMBER() OVER (ORDER BY LAST_UPDATE_DATE) rn
             FROM   acc_balance_stg
             WHERE  accounting_period='MAY-10')
      WHERE rn <= 100)
SELECT *
FROM   subq_bal bal
,      acc_Segments_v_tst seg
where  BAL.NATURAL_ACCOUNT = SEG.SEGMENT_VALUE
AND    SEG.SEGMENT_COLUMN = 'SEGMENT99';However, the parentheses you use around comb_id make me question what your intention is here in the subquery?
Do you have multiple rows in ACC_BALANCE_STG for the same comb_id and last_update_date?
If so you may want to do a MAX on last_update_date, group by comb_id before doing the analytic restriction.
Edited by: DomBrooks on Jun 16, 2010 5:56 PM