RE: oracle can ignore hints

  • From: April Wells <AWells@xxxxxxxxxx>
  • To: "'oracle-l@xxxxxxxxxxxxx'" <oracle-l@xxxxxxxxxxxxx>
  • Date: Thu, 4 Mar 2004 13:44:40 -0600

Yep, they are 'friendly suggestions' that the CBO can simply choose to
ignore if it thinks it knows better than you.

We have one query that we have hinted, we have computed statistics, we have
built histograms, we have jumped through hoops... the only way to force it
to use an index is to Never analyze that index and to hope, then, that the
CBO makes the right assumptions.

April Wells
Oracle DBA/Oracle Apps DBA
Corporate Systems
Amarillo Texas
"Few people really enjoy the simple pleasure of flying a kite"
Adam Wells age 11
"Imagination is the highest kite one can fly."
Lauren Bacall 

-----Original Message-----
From: ryan.gaffuri@xxxxxxx [mailto:ryan.gaffuri@xxxxxxx]
Sent: Thursday, March 04, 2004 12:44 PM
To: oracle-l@xxxxxxxxxxxxx
Subject: oracle can ignore hints

We had a discussion on here regarding hints. some of you stated that Oracle
cannot ignore a proper hint. I have a TAR open and asked about this. Here is
the response.

"A hint simply adds weight to a cost estimation, it can still be overridden
by the CBO if the values aren't seen as useful."

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