Re: Operationalize orthogonality
Date: 4 Jun 2006 23:33:27 -0700
Message-ID: <1149489207.098512.218820_at_c74g2000cwc.googlegroups.com>
Tony D wrote:
> mAsterdam wrote:
> >
> > It is imperative for any practical solution (i.e. with indexing)
> > that ordering operators (<, >) of a type can be communicated.
>
> I think this needs to be handled on a type-by-type basis; some types
> may not be amenable to ordering (types that generate other types, say
> ?)
> Also, types that you may want to use in non-equi joins.
Note that one can consider a non-equijoin as an equijoin on 0 attributes with a further join on the non-equality relation. Equijoin is fundamental; non-equijoin is not.
> At the end
> of the day, the restrict and join operators really don't care; they can
> hand off evaluation of the comparisons to operators you've defined, and
> as long as they return a boolean result that's fine. (Which might lead
> to the "!!!" up ahead ...)
Agreed.
> > > However, there's a great big "!!!" sign on the road ahead; can you
> > > guess what it is yet ?
> >
> > I am looking for them. Please share the one you see.
>
> In my last paragraph, I used this phrase :
>
> "they can hand off evaluation of the comparisons to operators you've
> defined, and as long as they return a boolean result that's fine."
>
> Think about this a little further, with specific reference to complex,
> structure types (and RVAs especially). The relational model may offer a
> get-out clause, though.
Marshall Received on Mon Jun 05 2006 - 08:33:27 CEST