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Home -> Community -> Mailing Lists -> Oracle-L -> RE: strange CBO decision
Rich
You don't mention the Oracle version. My recollection is that versions before 9i had no visibility to the bind variables. I think 9i has some, which some have termed "bind peek".
Dennis Williams
DBA
Lifetouch, Inc.
dwilliams_at_lifetouch.com
-----Original Message-----
From: oracle-l-bounce_at_freelists.org
[mailto:oracle-l-bounce_at_freelists.org]On Behalf Of Rich Holland
Sent: Monday, March 01, 2004 1:27 PM
To: oracle-l_at_freelists.org
Subject: strange CBO decision
I'm having a hard time figuring out why the CBO would choose this access
path.
I have an SAP table which contains HR data. The table contains the
following
fields in the first 2 columsn:
MANDT NOT NULL VARCHAR2(3) PERNR NOT NULl VARCHAR2(8)
The table's primary key contains both fields (plus a few more).
When I run an update using:
update pa0002 set field = 'value' where mandt = 100 and pernr = 00000001;
I would expect the system to do an index range scan over the primary key to
identify the rows which need updating, but it does a FTS instead. If I
specify
the value for MANDT in a bind variable, or even specify it as '100' instead
of
100 (i.e. quote it), the optimizer uses the index.
Anyone have any idea why specifying a specific numeric value vs. specifying
the
value via a bind variable or quoting it would trigger the FTS? I'm doing
the
update via Perl & DBI::Oracle 1.6, but that shouldn't matter...
Thanks!
Rich
--
Rich Holland (913) 645-1950 SAP Technical Consultant
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