Re: Best course to understand why a bad plan is chosen by optimizer
Date: Mon, 23 Sep 2019 20:35:33 -0400
Message-ID: <0fdab82c-5015-c4f6-8bd2-8155b992039f_at_gmail.com>
On 9/23/19 8:30 PM, Chris Taylor wrote:
> Then we get I to the whole "what does COST even mean" when costing the
> same query but yet costs can't be compared.
>
> I honestly think [sometimes? Often?] that Oracle has 'lost the plot'
> when it comes to the CBO.
>
> Chris
>
>
>
> On Mon, Sep 23, 2019, 7:08 PM Clay Jackson (cjackson)
> <Clay.Jackson_at_quest.com <mailto:Clay.Jackson_at_quest.com>> wrote:
>
> As usual, Mark "hit the nail on the head!". If all Cost
> Accountants thought and acted as he proposes, I would
> wholeheartedly agree. Unfortunately, reality and human nature
> often intrude, and I think THAT's where the issues come in. Far
> too many times, I've seen decisions made on the basis of "least
> hard dollar cost", w/o considering the "hidden" or "soft" costs.
>
> One great example of that, WITHOUT starting a whole discussion on
> "outsourcing" was the decision a former employer of mine made to
> outsource "Account Provisioning" and "Security".
>
> They told the displaced employees, "You have six months to train
> your replacements REMOTELY" (i.e., they did NOT spend the money to
> bring the "new" employees from the "low cost location" (the
> specific location, other than the fact that it was 8 timezones
> away, is really irrelevant) to the location of the current
> employees or vice-versa). When they executed the switch, the
> time to provision a new account went from 6 hours to 3 days, as
> the new folks learned all of "tribal knowledge" "the hard way"';
> and the error rate went from less than 1% rework to close to 75%
> rework.
>
> Clay Jackson
> Database Solutions Sales Engineer
> clay.jackson_at_quest.com <mailto:clay.jackson_at_quest.com>
> office 949-754-1203 mobile 425-802-9603
>
>
> -----Original Message-----
> From: Mark W. Farnham <mwf_at_rsiz.com <mailto:mwf_at_rsiz.com>>
> Sent: Monday, September 23, 2019 2:35 PM
> To: 'Mladen Gogala' <gogala.mladen_at_gmail.com
> <mailto:gogala.mladen_at_gmail.com>>; Clay Jackson (cjackson)
> <Clay.Jackson_at_quest.com <mailto:Clay.Jackson_at_quest.com>>;
> oracle-l_at_freelists.org <mailto:oracle-l_at_freelists.org>
> Subject: RE: Best course to understand why a bad plan is chosen by
> optimizer
>
> CAUTION: This email originated from outside of the organization.
> Do not follow guidance, click links, or open attachments unless
> you recognize the sender and know the content is safe.
>
>
> Blush (okay, I don't really do that, but, thanks.)
>
> Clay: Permission for re-use granted. I at least think that was
> original to me.
>
> Mladen, likewise, and further I suspect that *mostly* when we
> disagree we're looking at different pieces of the elephant.
>
> As for cost accounting the only thing I'm sure about is that it
> would be done better if we didn't tax corporations and have to
> legally mesh those views of the books.
> But I don't want to get into an argument about how corporate taxes
> are paid by customers on this technical forum, so I'll drop that
> without further wind.
>
> Of course meshing strategic provisioning with cost accounting as a
> check on predictions is a useful component of achieving the
> business goal of computer systems: 1) Reliable and quick enough
> most of the time to meet service delivery promises to customers,
> safe and recoverable enough to provide transaction integrity
> (which can be quite expensive to lose), and all done reasonably
> close to the minimum cost (where reasonably is where it would have
> cost more to plan better to reach a lower cost than the difference.)
>
> Experience guides toward erring a bit on the side of extra
> engineering to avoid expensively retooling too much too often. I
> think that newfangled method calls that "re-work." Experience also
> guides toward getting started sometime well before the last
> possible outcome is modelled and tested in a simulator (which is
> probably only justified rarely.)
>
> I'll take both of you as my allies if ever the opportunity crops
> up. And Lothar, too.
>
> mwf
>
> -----Original Message-----
> From: Mladen Gogala [mailto:gogala.mladen_at_gmail.com
> <mailto:gogala.mladen_at_gmail.com>]
> Sent: Monday, September 23, 2019 2:45 PM
> To: Clay Jackson (cjackson); mwf_at_rsiz.com <mailto:mwf_at_rsiz.com>;
> oracle-l_at_freelists.org <mailto:oracle-l_at_freelists.org>
> Subject: Re: Best course to understand why a bad plan is chosen by
> optimizer
>
> Hi Clay!
>
> Comments in line:
>
> On 9/23/19 1:19 PM, Clay Jackson (cjackson) wrote:
> > I've known Mark for a LONG time, and have ALWAYS been impressed
> with his elegant "turn of phrase"!
>
> I have never met Mark in my life and I am deeply sorry about it. I
> am following his contributions on various Oracle forums with a
> sort of fascination. I respect hist opinion deeply, even when I
> disagree with him.
>
>
> >
> >
> > I'm going to save this; and, with permission of course, may use
> it a few talks (I'm doing one in Dallas in a few weeks on "The
> Future of the DBA in a World of Autonomous Databases").
>
> Databases are extremely complex, even if autonomous. I don't
> envision being able to utilize a serious business database without
> having a DBA anytime soon. Also, databases are getting larger.
> Backup and recovery of
> 50+ TB database is not as simple as it may look. Look at the databases
> as modern airplanes. No robot can do what Sully Sullenberger has done.
> Auto-pilot is available for the long time but I would be very
> hesitant to fly an airplane which doesn't have a pilot on board.
>
> >
> > I think sometimes we forget the "Engineering" ; and I'm 100%
> certain my mother was correct, when, in 1970, she predicted "Cost
> Accounting will be the ruin of civilization".
>
> With all due respect, I disagree with your mother. Cost accounting
> is a necessary evil. You can call me crazy, but I prefer the money
> to be spent on my bonus over buying unnecessary software. My bonus
> is never unnecessary.
>
>
> >
> > Clay Jackson
> > Database Solutions Sales Engineer
> > clay.jackson_at_quest.com <mailto:clay.jackson_at_quest.com>
> > office 949-754-1203 mobile 425-802-9603
>
>
-- Mladen Gogala Database Consultant Tel: (347) 321-1217 -- http://www.freelists.org/webpage/oracle-lReceived on Tue Sep 24 2019 - 02:35:33 CEST