Qeury not using the bitmap index

Question

Hi,
Pls have a look at the query below:
SELECT
A.flnumber,
A.fldate,
SUBSTR(C.sec,1,3) sect,
D.element,
C.class,
SUM(C.qty) qty,
A.indicator,
DECODE(A.indicator, 'I', B.inrt, 'O', B.outrt, 'R', B.rting, NULL) direction,
B.rting
FROM
Header A,
Paths B,
PathData C,
ElementData D
WHERE
(D.category='N') AND
(A.rt=B.rt) AND
(C.element=D.element) AND
(A.fldate=C.fldate AND
A.flnumber=C.flnumber) AND
C.element IN (SELECT codes FROM Master_codes WHERE type='F')
GROUP BY A.flnumber,
     A.fldate,
     SUBSTR(C.sec, 1, 3),
     D.element,
     C.class,
     A.indicator,
     DECODE(A.indicator,'I', B.inrt, 'O', B.outrt,'R', B.rting, NULL),
B.rting
UNION ALL
SELECT
A.flnumber,
A.fldate,
SUBSTR(C.sec,1,3) sect,
D.element,
C.class,
SUM(C.qty) qty,
A.indicator,
DECODE(A.indicator, 'I', B.inrt, 'O', B.outrt, 'R', B.rting, NULL) ROUTE_direction,
B.rting
FROM
Header A,
Paths B,
PathData C,
ElementData D
WHERE
(D.category='N') AND
(A.rt=B.rt) AND
(C.element=D.element) AND
(A.fldate=C.fldate AND
A.flnumber=C.flnumber) AND
C.element NOT IN (SELECT codes FROM Master_codes WHERE type='F')
GROUP BY A.flnumber,
     A.fldate,
     SUBSTR(C.sec, 1, 3),
     D.element,
     C.class,
     A.indicator,
     DECODE(A.indicator,'I', B.inrt, 'O', B.outrt,'R', B.rting, NULL),
B.rting
The cost in the explain plan is very high. The table PathData* has 42710366 records and there is a bitmap index on the flnumber_ and fldate* columns. But the query above does not use the indexes. The other tables in the list are fine as their respective PK and indexes are used but the table PathData* is going for a "Table Access by Local Index Rowid". dont know what it means but the cost for this is 7126 which is high. I cant figure out why is the query not using the bitmap indexes for this table.
Pls let me know what should be done.???

Answer 1

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SELECT a.flnumber,
       a.fldate,
       Substr(c.sec, 1, 3)       sect,
       d.element,
       c.class,
       SUM(c.qty)                qty,
       a.INDICATOR,
       Decode(a.INDICATOR, 'I', b.inrt,
                           'O', b.outrt,
                           'R', b.rting,
                           NULL) direction,
       b.rting
FROM   header a,
       paths b,
       pathdata c,
       elementdata d
WHERE  ( d.category = 'N' )
       AND ( a.rt = b.rt )
       AND ( c.element = d.element )
       AND ( a.fldate = c.fldate
             AND a.flnumber = c.flnumber )
       AND c.element IN (SELECT codes
                         FROM   master_codes
                         WHERE  TYPE = 'F')
GROUP  BY a.flnumber,
          a.fldate,
          Substr(c.sec, 1, 3),
          d.element,
          c.class,
          a.INDICATOR,
          Decode(a.INDICATOR, 'I', b.inrt,
                              'O', b.outrt,
                              'R', b.rting,
                              NULL),
          b.rting
UNION ALL
SELECT a.flnumber,
       a.fldate,
       Substr(c.sec, 1, 3)       sect,
       d.element,
       c.class,
       SUM(c.qty)                qty,
       a.INDICATOR,
       Decode(a.INDICATOR, 'I', b.inrt,
                           'O', b.outrt,
                           'R', b.rting,
                           NULL) route_direction,
       b.rting
FROM   header a,
       paths b,
       pathdata c,
       elementdata d
WHERE  ( d.category = 'N' )
       AND ( a.rt = b.rt )
       AND ( c.element = d.element )
       AND ( a.fldate = c.fldate
             AND a.flnumber = c.flnumber )
       AND c.element NOT IN (SELECT codes
                             FROM   master_codes
                             WHERE  TYPE = 'F')
GROUP  BY a.flnumber,
          a.fldate,
          Substr(c.sec, 1, 3),
          d.element,
          c.class,
          a.INDICATOR,
          Decode(a.INDICATOR, 'I', b.inrt,
                              'O', b.outrt,
                              'R', b.rting,
                              NULL),
          b.rting  Edited by: sb92075 on Mar 13, 2011 7:58 AM