Re: satisfies algorithm

"Brian Selzer" <brian_at_selzer-software.com> wrote in message news:wRRik.17363$89.1080_at_nlpi069.nbdc.sbc.com...
>
> In nearly all of the commercial implementations and implementations of
> systems built with commercial implementations that pervade the industry,
> where there is a unique constraint or a primary key constraint that needs
> to be enforced, there is also an index. But thank you for pointing out
> that there are alternatives to using indexes without also providing the
> algorithms for those alternatives for the OP's edification. In other
> words, "where's the beef?" Can you back up your claims with more than
> marketing hype? I read the white papers Netezza provided on their web
> site, but I didn't feel a thrill going up my leg, if you know what I mean.
> Can you provide links to academic papers that describe these alteratives
> in detail. I'm curious, and I would bet that others here are too.
>
> By the way, how Netezza is implemented internally is anyone's guess. They
> may sort active domains--storing them in a particular order. Who knows?
> but wouldn't that be similar enough to be considered a facsimilie of an
> index?
>
> --Brian
>
>

I had hoped I wouldn't need to explain that it is possible to validate uniqueness without an index. For example some DBMSs will allow you to use a trigger or an assertion to enforce uniqueness. An index is simply a method for speeding that process up. In any case I don't expect discussions about fundamental matters to be limited to what "nearly all of the [current] commercial implementations" can support. The facts are what they are regardless of what Microsoft, Oracle, et al are selling. A key is a logical construct and an index is a physical one.

I'm really not sure what "claims" you want me to back up since you've already agreed that an index isn't always required (quote: "In nearly all..."). If you mean you want to know about optimisation strategies that don't involve indexes then you could start here: http://tods.acm.org/. There is a wealth of material on optimisation. Optimisation has nothing to do with keys of course, which brings us back to where we started...

-- 
David Portas