Re: Mysterious FILTER operation ;)

  • From: "Jonathan Lewis" <jonathan@xxxxxxxxxxxxxxxxxx>
  • To: <oracle-l@xxxxxxxxxxxxx>
  • Date: Mon, 3 Jan 2005 21:05:30 -0000

As far as the logical I/O goes, I would guess 
that the execution plan you are seeing from 
explain plan is NOT the plan that is actually 
occurring for CBO - bind variable peeking 
is probably switching you to a full tablescan.

The filter operation is probably similar to 
the type of filter that used to precede the
parts of partition views which were not
executed - in other words a constant
test that could pre-empt the execution 
of the child portions of the plan.  If your
specific plan has to be generated once with 
bind variables, then there has to be a mechanism 
that stops the real work being done when the
first variable is larger than the second variable
at run-time.

Regards

Jonathan Lewis

http://www.jlcomp.demon.co.uk/faq/ind_faq.html
The Co-operative Oracle Users' FAQ

http://www.jlcomp.demon.co.uk/seminar.html
Public Appearances - schedule updated Dec 23rd 2004






----- Original Message ----- 
From: <J.Velikanovs@xxxxxxxx>
To: <oracle-l@xxxxxxxxxxxxx>
Sent: Monday, January 03, 2005 6:19 PM
Subject: Mysterious FILTER operation ;)


Win2000 9.2.0.6 (tested on 9.2.0.4/SPARC Solaris as well)
FULL TEST text see at the end of letter.
I just trying to understand what FILTER operation doing in case described 
below.
I have ran the same SQL two times (with and without stats, CBO/RBO)


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