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RE: Why partition pruning is not happening?

From: Polarski, Bernard <Bernard.Polarski_at_atosorigin.com>
Date: Fri, 5 Jan 2007 14:03:06 +0100
Message-ID: <25D4919915CCF742A88EE3366D6D913D113D185D@mailserver1>


Partitioned on FE_DIA with an additional filter on ID_MES.  

When the CBO creates the plan, how should he knows that ID_MES is always a logical subset within FE_DIA?

There is not transitive predicate between FE_DIA and ID_MES and ID_MES is not organized as a ranged sub-partition of FE_DIA.  

As it is :  

a11.fe_dia = a12.fe_dia is a join condition that could be satisfied by all partitions and

a12.id_mes = 200611 Is a filter that could be true in any partitions.      

Bernard Polarski  

From: LS Cheng [mailto:exriscer_at_gmail.com] Sent: vrijdag 5 januari 2007 13:19
To: ORACLE-L
Subject: Why partition pruning is not happening?  

Hi

I have a DWH query which IMHO should do partition prunning but it does not. The query is as follows:

SELECT   a11.id_tp_busq id_tp_busq,
         a14.dt_busqueda dt_busqueda,
         a11.id_site id_site,
         a13.de_site de_site,
         SUM (a11.nt_busqueda) wjxbfs1
    FROM prm_fedia a12,
         prm_site a13,
         prm_tibusqbrs a14,
         prh_bqbusq a11     -- PARTITIONED BY FE_DIA 
   WHERE a11.fe_dia = a12.fe_dia
     AND a11.id_site = a13.id_site
     AND a11.id_tp_busq = a14.id_tp_busq
     AND a12.id_mes = 200611
     AND a13.id_site = 1
     AND a11.tx_termino LIKE 'Without usage%' 
GROUP BY a11.id_tp_busq, a14.dt_busqueda, a11.id_site, a13.de_site


| Id | Operation | Name |
Rows | Bytes | Cost | Pstart| Pstop |


| 0 | SELECT STATEMENT | |
2 |   154 |   113 |       |       | 

| 1 | SORT GROUP BY | |
2 | 154 | 113 | | |
| 2 | NESTED LOOPS | |
2 | 154 | 110 | | |
| 3 | NESTED LOOPS | |
2 | 130 | 108 | | |
| 4 | NESTED LOOPS | |
2 | 104 | 106 | | |
| 5 | TABLE ACCESS BY INDEX ROWID | PRM_SITE |
1 | 17 | 1 | | | |* 6 | INDEX UNIQUE SCAN | PRM_SITE_PK | 221 | | | | |
| 7 | PARTITION RANGE ALL | |
| | | 1 | 25 |
|* 8 | TABLE ACCESS BY LOCAL INDEX ROWID| PRH_BQBUSQ | 2 | 70 | 105 | 1 | 25 | |* 9 | INDEX RANGE SCAN | PRH_BQBUSQ_LN3 | 100 | | 50 | 1 | 25 | |* 10 | TABLE ACCESS BY INDEX ROWID | PRM_FEDIA | 1 | 13 | 1 | | | |* 11 | INDEX UNIQUE SCAN | PRM_FEDIA_PK | 85 | | | | |
| 12 | TABLE ACCESS BY INDEX ROWID | PRM_TIBUSQBRS |
1 | 12 | 1 | | | |* 13 | INDEX UNIQUE SCAN | PRM_TIBUSQBRS_PK | 1 | | | | | ------------------------------------------------------------------------ ------------------------------------

Predicate Information (identified by operation id):


   6 - access("A13"."ID_SITE"=1)
   8 - filter("A11"."ID_SITE"=1) 
   9 - access("A11"."TX_TERMINO" LIKE 'Without usage%')
       filter("A11"."TX_TERMINO" LIKE 'Without usage%')
  10 - filter("A12"."ID_MES"=200611) 

  11 - access("A11"."FE_DIA"="A12"."FE_DIA")   13 - access("A11"."ID_TP_BUSQ"="A14"."ID_TP_BUSQ")

I was expecting the condition a11.fe_dia = a12.fe_dia eliminates partitions and only reads 2006 November Partition. Any clues why it is not happening...?

This is 9.2.0.4 running on HPUX

Cheers

--
LSC 





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Received on Fri Jan 05 2007 - 07:03:06 CST

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