RE: rm RULE based optimizer != GOOD IDEA
- From: "Michael Fontana" <mfontana@xxxxxxxxx>
- To: <oracle-l@xxxxxxxxxxxxx>
- Date: Mon, 25 Apr 2005 11:01:19 -0500
What we have found in our shop, where we have tons of purchased products and
have just implemented Siebel's first CBO release, is that you have to get
down to the nuts and bolts details of your problem queries. Once you do,
you will often find that your statistics are flawed, which in turn causes a
few (sometimes often critically) poor performing queries.
Some examples -
A batch process loads a million rows to a table but doesn't regenerate
stats.
Solution: Stats are stale - there is now an option in the optimizer to
detect this and regenerate them.
Cardinality stats are not granular enough for a large, key table.
Solution: Run stats for specific tables with parms to selectively drill
down and return the correct information for such tables.
It may be a lot of work, but we've been able to run CBO for several major
apps (both in-house and third party) including Siebel, SAP, Peoplesoft and
Oracle Apps, without resorting to the RBO rule "copout".
And we've had numerous development consultants try to sneak them in.
We simply won't allow it.
Over the long haul, it will cost still more time and money to repair the
downstream damage....
-----Original Message-----
From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx]
On Behalf Of Post, Ethan
Sent: Friday, April 22, 2005 12:50 PM
To: Lex de Haan; thomas.mercadante@xxxxxxxxxxxxxxxxx; Pete Sharman;
Christian Antognini
Cc: oracle-l@xxxxxxxxxxxxx
Subject: RE: rm RULE based optimizer != GOOD IDEA
If you head over to http://channel9.msdn.com you might be able to find a
video (a month or two ago I think) which is a tour of SQL Server's
automated testing facility, it is pretty impressive.
-----Original Message-----
From: Lex de Haan [mailto:lex.de.haan@xxxxxxxxxxxxxx]=20
Sent: Friday, April 22, 2005 12:39 PM
To: thomas.mercadante@xxxxxxxxxxxxxxxxx; Post, Ethan; 'Pete Sharman';
'Christian Antognini'
Cc: oracle-l@xxxxxxxxxxxxx
Subject: RE: rm RULE based optimizer !=3D GOOD IDEA
you don't have the faintest idea about the size and complexity of
Oracle's
regression tests,
and the frequency they run with ... bug-free software is an utopia.
kind regards,
Lex.
=20
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