Re: In an RDBMS, what does "Data" mean?

In message <AwJxc.378$Pt.303_at_newssvr19.news.prodigy.com>, Eric Kaun <ekaun_at_yahoo.com> writes
>"Anthony W. Youngman" <wol_at_thewolery.demon.co.uk> wrote in message
>news:LnpFiHNqXPxAFwgC_at_thewolery.demon.co.uk...
>> In message <kH4wc.5267$n65.660_at_newssvr33.news.prodigy.com>, Eric Kaun
>> <ekaun_at_yahoo.com> writes
>
>> relational actually
>> prevents you from even trying to prove the question is easy, merely
>> saying "you have no choice but to trust the optimiser" :-(
>
>Huh? Prove the question is easy? What does that mean?
>
>At any level above hardware, we have no choice - it depends on the
>processor, and hard disk, and memory speed, and... so of course there's a
>level of trust involved. Do you trust the Pick compiler / interpreter? I
>certainly want to delegate the nasty business of optimization (which we've
>demonstrated is useful in the considerably more-difficult area of compilers)
>to a machine which can do the job better and faster than I.
>
Basically, if we assume (reasonable assumption) that everything else is irrelevant when compared to disk access, I can prove that (almost) every attempted disk access actually retrieves data that is relevant to the question.

I can also show statistically that the chances of retrieving multiple items of interest with a single access are also high.

Of course, that argument is less relevant now we have huge amounts of ram...

Cheers,
Wol

-- 
Anthony W. Youngman - wol at thewolery dot demon dot co dot uk
HEX wondered how much he should tell the Wizards. He felt it would not be a
good idea to burden them with too much input. Hex always thought of his reports
as Lies-to-People.
The Science of Discworld : (c) Terry Pratchett 1999