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Home -> Community -> Mailing Lists -> Oracle-L -> Re: Re: Explain plan accuracy and bind variables
what about autotrace? that occurs after the query is run? =
> =
> From: Connor McDonald <hamcdc_at_yahoo.co.uk>
> Date: 2004/02/06 Fri AM 08:18:49 EST
> To: oracle-l_at_freelists.org
> 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_at_cox.net 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? =
> > =
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> =
> =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_at_yahoo.com
> =
> "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"
> =
> =
> =
> =
> =
> ___________________________________________________________
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-- Archives are at http://www.freelists.org/archives/oracle-l/ FAQ is at http://www.freelists.org/help/fom-serve/cache/1.html -----------------------------------------------------------------Received on Fri Feb 06 2004 - 07:36:40 CST
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