Re: Explain plan accuracy and bind variables
- From: Daniel Fink <Daniel.Fink@xxxxxxx>
- To: oracle-l@xxxxxxxxxxxxx
- Date: Fri, 06 Feb 2004 08:36:32 -0700
Could we see it?
Cary Millsap wrote:
> Nevermind; I've done it.
>
> Cary Millsap
> Hotsos Enterprises, Ltd.
> http://www.hotsos.com
> * Nullius in verba *
>
> Upcoming events:
> - Performance Diagnosis 101: 2/24 San Diego, 3/23 Park City, 4/6 Seattle
> - SQL Optimization 101: 2/16 Dallas
> - Hotsos Symposium 2004: March 7-10 Dallas
> - Visit www.hotsos.com for schedule details...
>
> -----Original Message-----
> From: oracle-l-bounce@xxxxxxxxxxxxx
> [mailto:oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of Cary Millsap
> Sent: Friday, February 06, 2004 9:02 AM
> To: oracle-l@xxxxxxxxxxxxx
> Subject: RE: Re: Explain plan accuracy and bind variables
>
> Can someone provide an example of a query that emits STAT lines that
> contradict the output of EXPLAIN PLAN because of the use of bind
> variables?
>
> Cary Millsap
> Hotsos Enterprises, Ltd.
> http://www.hotsos.com
> * Nullius in verba *
>
> Upcoming events:
> - Performance Diagnosis 101: 2/24 San Diego, 3/23 Park City, 4/6 Seattle
> - SQL Optimization 101: 2/16 Dallas
> - Hotsos Symposium 2004: March 7-10 Dallas
> - Visit www.hotsos.com for schedule details...
>
> -----Original Message-----
> From: oracle-l-bounce@xxxxxxxxxxxxx
> [mailto:oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of ryan.gaffuri@xxxxxxx
> Sent: Friday, February 06, 2004 7:37 AM
> To: oracle-l@xxxxxxxxxxxxx
> Subject: Re: Re: Explain plan accuracy and bind variables
>
> what about autotrace? that occurs after the query is run? =
>
> > =
>
> > From: Connor McDonald <hamcdc@xxxxxxxxxxx>
> > Date: 2004/02/06 Fri AM 08:18:49 EST
> > To: oracle-l@xxxxxxxxxxxxx
> > Subject: Re: Explain plan accuracy and bind variables
> > =
>
> > I think this comes the various methods people use to take an existing
> S=
> QL and attempt to determine
> > an explain plan.
> > =
>
> > eg you might see in a trace file a slow query
> > =
>
> > select * from table where col =3D :b1
> > =
>
> > You run this through explain plan and voila! Looks great - no problem.
> =
> But what really happened
> > on the live system was that 'col' was char, and :b1 was numeric, and
> th=
> us the index on 'col' was
> > not used. The execution plan in a trace file *will* be the one that
> wa=
> s used. This is quite
> > different to the plan you would see if you ran 'tkprod explain=3D..'
> > =
>
> > etc etc etc
> > =
>
> > hth
> > connor
> > =
>
> > --- ryan.gaffuri@xxxxxxx wrote: > I read somewhere that explain plans
> =
> are not always accurate.
> > Does this include autotrace? What
> > > about if I do a 10046 or just a sql_trace? =
>
> > > =
>
> > > Are explain plans more apt to be inaccurate with bind variables(I
> thi=
> nk I read that somewhere).
> > > If so, why? =
>
> > > =
>
> > > ----------------------------------------------------------------
> > > Please see the official ORACLE-L FAQ: http://www.orafaq.com
> > > ----------------------------------------------------------------
> > > To unsubscribe send email to: oracle-l-request@xxxxxxxxxxxxx
> > > put 'unsubscribe' in the subject line.
> > > --
> > > Archives are at //www.freelists.org/archives/oracle-l/
> > > FAQ is at //www.freelists.org/help/fom-serve/cache/1.html
> > > ----------------------------------------------------------------- =
>
> > =
>
> > =3D=3D=3D=3D=3D
> > Connor McDonald
> > Co-author: "Mastering Oracle PL/SQL - Practical Solutions" - available
> =
> now
> > web: http://www.oracledba.co.uk
> > web: http://www.oaktable.net
> > email: connor_mcdonald@xxxxxxxxx
> > =
>
> > "GIVE a man a fish and he will eat for a day. But TEACH him how to
> fish=
> , and...he will sit in a boat and drink beer all day"
> > =
>
> > =
>
> > =
>
> > =
>
> > =
>
> > ___________________________________________________________
> > BT Yahoo! Broadband - Free modem offer, sign up online today and save
> =A3=
> 80 http://btyahoo.yahoo.co.uk
> > ----------------------------------------------------------------
> > Please see the official ORACLE-L FAQ: http://www.orafaq.com
> > ----------------------------------------------------------------
> > To unsubscribe send email to: oracle-l-request@xxxxxxxxxxxxx
> > put 'unsubscribe' in the subject line.
> > --
> > Archives are at //www.freelists.org/archives/oracle-l/
> > FAQ is at //www.freelists.org/help/fom-serve/cache/1.html
> > -----------------------------------------------------------------
> > =
>
> ----------------------------------------------------------------
> Please see the official ORACLE-L FAQ: http://www.orafaq.com
> ----------------------------------------------------------------
> To unsubscribe send email to: oracle-l-request@xxxxxxxxxxxxx
> put 'unsubscribe' in the subject line.
> --
> Archives are at //www.freelists.org/archives/oracle-l/
> FAQ is at //www.freelists.org/help/fom-serve/cache/1.html
> -----------------------------------------------------------------
>
> ----------------------------------------------------------------
> Please see the official ORACLE-L FAQ: http://www.orafaq.com
> ----------------------------------------------------------------
> To unsubscribe send email to: oracle-l-request@xxxxxxxxxxxxx
> put 'unsubscribe' in the subject line.
> --
> Archives are at //www.freelists.org/archives/oracle-l/
> FAQ is at //www.freelists.org/help/fom-serve/cache/1.html
> -----------------------------------------------------------------
>
> ----------------------------------------------------------------
> Please see the official ORACLE-L FAQ: http://www.orafaq.com
> ----------------------------------------------------------------
> To unsubscribe send email to: oracle-l-request@xxxxxxxxxxxxx
> put 'unsubscribe' in the subject line.
> --
> Archives are at //www.freelists.org/archives/oracle-l/
> FAQ is at //www.freelists.org/help/fom-serve/cache/1.html
> -----------------------------------------------------------------
----------------------------------------------------------------
Please see the official ORACLE-L FAQ: http://www.orafaq.com
----------------------------------------------------------------
To unsubscribe send email to: oracle-l-request@xxxxxxxxxxxxx
put 'unsubscribe' in the subject line.
--
Archives are at //www.freelists.org/archives/oracle-l/
FAQ is at //www.freelists.org/help/fom-serve/cache/1.html
-----------------------------------------------------------------
Other related posts:
