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Re: Designing database tables for performance?

From: joel garry <joel-garry_at_home.com>
Date: 6 Mar 2007 15:21:20 -0800
Message-ID: <1173223279.677741.224630@c51g2000cwc.googlegroups.com>


On Mar 6, 12:52 pm, "Cimode" <cim..._at_hotmail.com> wrote:
> On 6 mar, 05:59, "d..._at_smooth1.co.uk" <d..._at_smooth1.co.uk> wrote:
>
>
>
> > On 24 Feb, 13:30, "Cimode" <cim..._at_hotmail.com> wrote:
>
> > > On 23 fév, 22:33, "jgar the jorrible" <joel-ga..._at_home.com> wrote:
>
> > > > > In what RAM would be less physical than HD ? For any reason, an
> > > > > absurdity is an absurdity.
>
> > > > Not an absurdity, you just aren't paying attention to how the I/O is
> > > > counted.
>
> > > So you say there are *ways* to count IO's. Fair enough. Question is:
> > > what has the way of counting IO's has any bearing on the media that
> > > supports them and therefore qualifies their nature as physical or
> > > logical? What is the difference: speed?
>
> > Yes. A logical I/O does not go down an I/O channel but comes via the
> > memory bus.
>
> And in what a memory bus is less *physical* than an IO channel? How
> do you think such bus is filled with data at some point in time
> otherwise than by a pull on the IO channel.

??? The whole point is that it might have been updated only in memory and may have nothing to do with I/O until some time in the future, or maybe never if it is rolled back.

You _really_ should read the Oracle concepts manual, as well as come into this century to see how modern databases deal with multiversion consistency. Thinking there is a one-to-one relationship between what is in memory and what is on disk is just stupid.

>
> > The time to complete is therefore far less and the "cost" in terms of
> > time is much less.
>
> So because time is the difference that makes less physical. Don't you
> see anything wrong in that?

Not at all. One defines the terms from a viewpoint. In this case, the viewpoint is "stuff that the Database has control over versus stuff the Operating System has control over."

If your theory can't deal with those concepts, it must not be a good theory. I'm sure we'll all readily concede the terminology won't make everyone happy, but that is no excuse for rejecting the terminology. That just anti-semanticism.

jg

--
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Received on Tue Mar 06 2007 - 17:21:20 CST

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