Re: Re: how to get oracle to ignore an index
- From: "Jonathan Lewis" <jonathan@xxxxxxxxxxxxxxxxxx>
- To: <oracle-l@xxxxxxxxxxxxx>
- Date: Fri, 6 Feb 2004 19:12:13 -0000
Notes in-line
Regards
Jonathan Lewis
http://www.jlcomp.demon.co.uk
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----- Original Message -----
From: <ryan.gaffuri@xxxxxxx>
To: <oracle-l@xxxxxxxxxxxxx>
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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