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RE: Oracle position on hints

From: MacGregor, Ian A. <ian_at_SLAC.Stanford.EDU>
Date: Mon, 10 Mar 2003 11:25:29 -0800
Message-ID: <F001.00564F21.20030310112529@fatcity.com>


Oh, I don't know. There is the FIRST_WIVES(1) hint which should always be employed. There is also the rules-based SWAMBOO (She Who Always Must BE Obeyed Optimization) mode. I'm sure others as well.

Congratulations Connor!

Ian MacGregor

-----Original Message-----
Sent: Saturday, March 08, 2003 8:49 PM
To: Multiple recipients of list ORACLE-L

 Congratulations!

 No hints for you:)  

 Regards,

 Waleed

-----Original Message-----
To: Multiple recipients of list ORACLE-L Sent: 3/8/03 8:53 PM

Just to add my meaningless diatribe to the discussion, I think that there are "good" hints and "bad" hints.

For example, first_rows(n) is a good hint, in that you are giving the optimizer more information as to what your motivations are for this query, without stifling it into a choice that may not be appropriate down the track.

Hints such as index(tab,idx) are "bad" hints, because you are more exposed to grief. If the index is renamed, then its no longer a hint. If the data distribution changes, or the index is rebuilt in reverse or compressed, then it may no longer be a good option, etc.

In terms of the vendor speak of "hints imply weak optimizer" I think thats nonsense. Having worked with DB2 in the past, nothing used to be more irritating then coming up with bizarre convolutions on an otherwise simple SQL to ensure that certain indexes were or were not chosen.

Cheers
Connor

PS - Its probably a little sad that I'm chit-chatting on hints on the morning of my wedding day, but hey, you gotta pass the time somehow whilst the other half is getting the hair and makeup done :-)


Connor McDonald
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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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Author: MacGregor, Ian A.
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Received on Mon Mar 10 2003 - 13:25:29 CST

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