Reason behind Difference in cardinality from estimation.

Question

Hi,
Below is the plan and the dbms_xplan.display_cursor out put for the same. I am getting difference in cardinality estimation which is major one. What must be the reason behind the same. i have verified that all the stats for index and table are updated.
SELECT
        XDS_XCHGTRANSACTIONID,
         XDS_TXSTATE,
         XDS_ACTIONDATE,
         XDS_INBOUND,
         XDS_DOCTYPE,
         XDS_DOCSUBTYPE
    FROM a, b, c   WHERE     b.XCHGPROFILEPK = a.XDS_XCHGPROFILEPK
         AND b.PAYID = c.PAYID
         AND a.XDS_TXSTATE IN ('PARTIAL', 'COMPLETE', 'PENDING')
         AND CREATINGAPP = 'DISB'
         AND COMPANYPK = 15144193056
         AND a.XDS_ACTIONDATE BETWEEN 1337890976198 AND 1338392336151
         AND a.XDS_YEAR IN 2012
         AND a.XDS_MONTH IN 5
ORDER BY a.XDS_ACTIONDATE
Index IDX_XDS_N1 is on a(XDS_MONTH,XDS_YEAR,XDS_ACTIONDATE)
| Id  | Operation                      | Name                    | Starts | E-Rows | A-Rows |   A-Time   | Buffers | Reads  |
|*  1 |  TABLE ACCESS BY INDEX ROWID   | c                       |      1 |      1 |      0 |00:00:00.68 |    2284 |    405 |
|   2 |   NESTED LOOPS                 |                         |      1 |      1 |      1 |00:00:00.68 |    2284 |    405 |
|   3 |    NESTED LOOPS                |                         |      1 |      1 |      0 |00:00:00.68 |    2284 |    405 |
|*  4 |     TABLE ACCESS BY INDEX ROWID| a                       |      1 |      1 |      0 |00:00:00.68 |    2284 |    405 |
|*  5 |      INDEX RANGE SCAN          | IDX_XDS_N1              |      1 |      1 |   2280 |00:00:00.12 |      30 |     28 |
|*  6 |     TABLE ACCESS BY INDEX ROWID| b                       |      0 |      1 |      0 |00:00:00.01 |       0 |      0 |
|*  7 |      INDEX UNIQUE SCAN         | P_XCHGPROFILE           |      0 |      1 |      0 |00:00:00.01 |       0 |      0 |
|*  8 |    INDEX RANGE SCAN            | IDX_PAYID               |      0 |      1 |      0 |00:00:00.01 |       0 |      0 |
Predicate Information (identified by operation id):
   1 - filter("COMPANYPK"=15144193056)
   4 - filter(("XDS_TXSTATE"='COMPLETE' OR "XDS_TXSTATE"='PARTIAL' OR "XDS_TXSTATE"='PENDING'))
   5 - access("XDS_MONTH"=5 AND "XDS_YEAR"=2012 AND "XDS_ACTIONDATE">=1337890976198 AND
              "XDS_ACTIONDATE"<=1338392336151)
   6 - filter("CREATINGAPP"='DISB')
   7 - access("XDS_XCHGPROFILEPK"="XCHGPROFILEPK")
   8 - access("B"."PAYID"="C"."PAYID")

Answer 1

930254 wrote:
Hi,
Below is the plan and the dbms_xplan.display_cursor out put for the same. I am getting difference in cardinality estimation which is major one. What must be the reason behind the same. i have verified that all the stats for index and table are updated. Can't say based on what you have posted so far. Some suggestions/questions:
1) Do you get same difference if you simplify the query so that it includes only one table (i.e. a) with predicates on that table?
2) DB Version ?
3) Is XDS_ACTIONDATE supposed to be a date stored as NUMBER?