Why RBO might be better than CBO ?

Question

Hi ,
I have a query that references 4 base tables , indexes have been created and analyzed
but when using CBO it's is very slow and it's fast when using the RULE hints.
is this something to do with the logic of the query ?
pls advise
tks & rdgs

Answer 1

hi ,
fyi its the same queries with 2 mode
-- using CHOOSE
SELECT
  PT.PT_ID,
  PD_INST.CALL_PD_NAME,
  RCP.RCP_ID,
  RCP.RCP_TITLE,
  PD.PD_TITLE,
  RCP.EQP_TYPE
FROM
  PT,
  PD_INST,
  RCP,
  PD,
  PD_INST_RS
WHERE
  ( PT.PT_ID = PD_INST.PD_ID  )
  AND  ( PD.PD_ID = PD_INST_RS.PD_ID  )
  AND  ( (RCP.RCP_NAME = PD_INST_RS.RCP_NAME) AND (RCP.RCP_AF = 'A')  )
  AND  ( (PD.PD_ID LIKE PD_INST.CALL_PD_NAME || '.%') AND (PD.PD_AF = 'A')  )
  AND  (
  ( PT.PT_AF = 'A'  )
  AND  ( PT.OF <> 'Y'  )
  AND  ( PD.PD_AF = 'A'  )
  AND  ( PD.OF <> 'Y'  )
  AND  ( RCP.RCP_AF = 'A'  )
  AND  ( RCP.OF <> 'Y'  )
  AND  PD_INST.INST_NUM  =  'ab3e12'
  AND  ( PD_INST_RS.HIE = 'Y'  )
  AND  ( PD_INST_RS.MP = 'Y'  )
  AND  PT.PRODSTATUS  =  'A'
SELECT STATEMENT, GOAL = CHOOSE     Cardinality=1     Cost=268     Optimizer=CHOOSE     
TABLE ACCESS BY INDEX ROWID     Cardinality=139     Cost=2     Optimizer=ANALYZED     Object name=PD_INST
  NESTED LOOPS     Cardinality=1     Cost=268          
   MERGE JOIN CARTESIAN     Cardinality=4     Cost=267          
    TABLE ACCESS BY INDEX ROWID     Cardinality=1     Cost=3     Optimizer=ANALYZED     Object name=PD_INST_RS
     NESTED LOOPS     Cardinality=1     Cost=181          
      MERGE JOIN CARTESIAN     Cardinality=29     Cost=111          
       TABLE ACCESS FULL     Cardinality=1     Cost=25     Optimizer=ANALYZED     Object name=RCP
       BUFFER SORT     Cardinality=67     Cost=86          
        TABLE ACCESS FULL     Cardinality=67     Cost=86     Optimizer=ANALYZED     Object name=PD
      INDEX RANGE SCAN     Cardinality=227     Cost=3     Optimizer=ANALYZED     Object name=PD_INST_RS_PK
    BUFFER SORT     Cardinality=165     Cost=264          
     TABLE ACCESS FULL     Cardinality=165     Cost=86     Optimizer=ANALYZED     Object name=PT
   INDEX RANGE SCAN     Cardinality=1     Cost=2     Optimizer=ANALYZED     Object name=PD_INST_PK
-- using RULE
SELECT /*+ RULE */
  PT.PT_ID,
  PD_INST.CALL_PD_NAME,
  RCP.RCP_ID,
  RCP.RCP_TITLE,
  PD.PD_TITLE,
  RCP.EQP_TYPE
FROM
  PT,
  PD_INST,
  RCP,
  PD,
  PD_INST_RS
WHERE
  ( PT.PT_ID = PD_INST.PD_ID  )
  AND  ( PD.PD_ID = PD_INST_RS.PD_ID  )
  AND  ( (RCP.RCP_NAME = PD_INST_RS.RCP_NAME) AND (RCP.RCP_AF = 'A')  )
  AND  ( (PD.PD_ID LIKE PD_INST.CALL_PD_NAME || '.%') AND (PD.PD_AF = 'A')  )
  AND  (
  ( PT.PT_AF = 'A'  )
  AND  ( PT.OF <> 'Y'  )
  AND  ( PD.PD_AF = 'A'  )
  AND  ( PD.OF <> 'Y'  )
  AND  ( RCP.RCP_AF = 'A'  )
  AND  ( RCP.OF <> 'Y'  )
  AND  PD_INST.INST_NUM  =  'ab3e12'
  AND  ( PD_INST_RS.HIE = 'Y'  )
  AND  ( PD_INST_RS.MP = 'Y'  )
  AND  PT.PRODSTATUS  =  'A'
SELECT STATEMENT, GOAL = HINT: RULE               Optimizer=HINT: RULE     
TABLE ACCESS BY INDEX ROWID               Optimizer=ANALYZED     Object name=RCP
  NESTED LOOPS                    
   NESTED LOOPS                    
    NESTED LOOPS                    
     NESTED LOOPS                    
      TABLE ACCESS FULL               Optimizer=ANALYZED     Object name=PD_INST
      TABLE ACCESS BY INDEX ROWID               Optimizer=ANALYZED     Object name=PT
       INDEX UNIQUE SCAN               Optimizer=ANALYZED     Object name=PT_PK
     TABLE ACCESS BY INDEX ROWID               Optimizer=ANALYZED     Object name=PD
      INDEX RANGE SCAN               Optimizer=ANALYZED     Object name=PD_IK03
    TABLE ACCESS BY INDEX ROWID               Optimizer=ANALYZED     Object name=PD_INST_RS
     INDEX RANGE SCAN               Optimizer=ANALYZED     Object name=PD_INST_RS_PK
   INDEX RANGE SCAN               Optimizer=ANALYZED     Object name=RCP_NDX_1tks & rgds