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Re: Re: how to get oracle to ignore an index

From: <ryan.gaffuri_at_cox.net>
Date: Fri, 6 Feb 2004 14:30:58 -0500
Message-Id: <20040206193058.PNKB2432.lakemtao07.cox.net@smtp.central.cox.net>


ok thanks. I guess i mis-read the articles. got the hint you said was wrong out of the O'Reilly Oracle SQL Tuning handbook. I just double checked on OTN. My bad on that one.

thanks for the corrections.
>
> From: "Jonathan Lewis" <jonathan_at_jlcomp.demon.co.uk>
> Date: 2004/02/06 Fri PM 02:12:13 EST
> To: <oracle-l_at_freelists.org>
> Subject: Re: Re: how to get oracle to ignore an index
>
>
> Notes in-line
>
> Regards
>
> Jonathan Lewis
> http://www.jlcomp.demon.co.uk
>
> The educated person is not the person
> who can answer the questions, but the
> person who can question the answers -- T. Schick Jr
>
>
> Next public appearances:
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> March 2004 Charlotte NC OUG - CBO Tutorial
> April 2004 Iceland
>
>
> One-day tutorials:
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>
> ----- Original Message -----
> From: <ryan.gaffuri_at_cox.net>
> To: <oracle-l_at_freelists.org>
> Sent: Friday, February 06, 2004 6:28 PM
> Subject: Re: Re: how to get oracle to ignore an index
>
>
> i cant reproduce the data for you. its internal. I tested it repeatedly. I
> was very careful about the hint.
>
> select /*+ index(<index_name>) */
>
> >>> The thing above is not a valid hint
>
> select /*+ index(<table> <index_name>) */
>
> >>> The thing above might not be a valid hint
> >>> as the <table> might have been given an alias
> >>> If the table does not have an alias, then this
> >>> will be obeyed, unless some conditions relating
> >>> to null columns could make the indexed path
> >>> return the wrong path, or (prior to skip scans)
> >>> there was no optimizer mechanism for using
> >>> the index.
>
> Tried it repeatedly. I've seen it before. Sorry, I cant show you the data,
> etc... I could have swarn I read in the docs that hints are just directives
> and oracle does not have to use them? I cant find it right now. Am I wrong?
> I'm pretty sure I have seen that several times.
>
> >>> There are some bugs relating to execution methods
> >>> that require some detailed examination of 10053
> >>> trace files to determine how Oracle pushed an
> >>> 'obvious' hint out of context. Apart from these,
> >>> and there are some 'feature-related' hints that
> >>> can only work if various init.ora parameters
> >>> are set ... and so on.
> >>>
> >>> You probably have read that hints are 'just'
> >>> directives (to me a directive is the same as
> >>> an order, by the way). I've seen it in a Metalink
> >>> note somewhere. You will have found numerous
> >>> articles which say that hints can be ignored.
> >>> But in recent versions I don't think I've been
> >>> presented with an example where a valid hint
> >>> was ignored.
> >>
>
>
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Received on Fri Feb 06 2004 - 13:30:58 CST

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