Re: need enhance feature for CBO :)

From: John D Parker <orclwzrd_at_yahoo.com>
Date: Tue, 11 Nov 2008 07:32:48 -0800 (PST)
Message-ID: <350316.34051.qm@web32607.mail.mud.yahoo.com>

you have an IOT with the leading edge being AN and a unique index with the leading edge being SEQ.

The question you asked of the database is give me all the distinct SEQ numbers. The fastest way to do that is to full scan the unique index with SEQ on the leading edge. There is no structure that specifically indexes the partition key unless you build it.

Tom Kyte(Expert one on one oracle) and Jonathan Lewis(practical oracle8i) both have good chapters on partitioning in their books. A quick review of one or both will help lots. Both books though not "10g" have very good explanations of how partitioning works and how to take full advantage of partitioning.

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From: Ujang Jaenudin <ujang.jaenudin_at_gmail.com> To: Oracle Discussion List <oracle-l_at_freelists.org>; indo-oracle_at_yahoogroups.com Sent: Tuesday, November 11, 2008 4:49:26 AM Subject: need enhance feature for CBO :)

dear all, (sorry cross posting)

oracle 10.1.0.5
huge machine :)

CREATE TABLE PVC
(

  ........
  CONSTRAINT PVC_PK
PRIMARY KEY
(AN, SEQ, ES, ETI, ER)

)
ORGANIZATION INDEX <=== IOT :(
  PARTITION BY RANGE (SEQ)
........... (500 partitions even more)
)
NOPARALLEL; CREATE UNIQUE INDEX PVC_U1 ON PVC
(SEQ, ER)

LOCAL (
............ (500 partitions even more)
)
NOPARALLEL; there are more than billion of rows

select /*+ use_index(pvc pvc_pk) */ distinct seq from pvc;

SELECT STATEMENT ALL_ROWS
   PARTITION RANGE ALL

      SORT UNIQUE NOSORT
         INDEX FULL SCAN INDEX(UNIQUE) PVC_U1

so, my question:
- why don't oracle utilize "partition key" for this case....   (by not scanning full index will be better, because partition key based on SEQ column).
  getting list of partition key is the fastest way :) - even when force using PVC_PK, CBO won't do it, I think scanning Primary key   more efficient rather than roundtrip read PVC_U1 index and then again   read PVC_PK index, due to IOT mapping...

-- 
thanks and regards
ujang | oracle dba
jakarta | http://ora62.wordpress.com
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Received on Tue Nov 11 2008 - 09:32:48 CST