RE: Filter operation

  • From: "Brooks, Dominic (London)(c)" <dbrooks@xxxxxxxxxxxxxxxxxx>
  • To: <exriscer@xxxxxxxxx>, "Oracle Mailinglist" <oracle-l@xxxxxxxxxxxxx>
  • Date: Tue, 23 Mar 2010 15:03:20 -0000

SYSDATE has to be evaluated at execution time not parse time hence the
KEY pstart/pstop plan and the FILTERs.
With the literals, the optimizer knows at parse time which partitions
are involved.
So, you say that you don't get the FILTER operations, but I expect you
also get non KEY pstart/pstop.


From: oracle-l-bounce@xxxxxxxxxxxxx
[mailto:oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of LS Cheng
Sent: 23 March 2010 14:45
To: Oracle Mailinglist
Subject: Filter operation

Hi all

I have this following query

    WHERE MF.F_PERIOD >= add_months(trunc(sysdate, 'MM'), -1)
      AND MF.F_PERIOD < trunc(sysdate, 'MM')

shows this plan:

| Id  | Operation                  |  Name             | Rows  | Bytes |
Cost  | Pstart| Pstop |
|   0 | SELECT STATEMENT           |                   | 17641 |   189K|
17182 |       |       |
|   1 |  SORT GROUP BY             |                   | 17641 |   189K|
17182 |       |       |
|*  2 |   FILTER                   |                   |       |       |
|       |       |
|   3 |    PARTITION RANGE ITERATOR|                   |       |       |
|   KEY |   KEY |
|*  4 |     TABLE ACCESS FULL      | TB_MESURE_EO_GLA  |  5449K|    57M|
12941 |   KEY |   KEY |

Predicate Information (identified by operation id):

   2 -
   4 - filter("MF"."F_PERIOD">=ADD_MONTHS(TRUNC(SYSDATE@!,'fmmm'),-1)

There is a filter operation which is making this query pretty slow, if I
change add_months and trunc(sysdate) to literals such as 

to_date('20100201 00:00:00', 'yyyymmdd hh24:mi:ss')
to_date('20100301 00:00:00', 'yyyymmdd hh24:mi:ss')

The filter operation no longer exists.

I wonder the need of a filter operation when functions are used? 

Any suggestions?



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