Re: Object-relational impedence

On Mar 5, 9:31 am, S Perryman <q..._at_q.net> wrote:
> Marshall wrote:
> > On Mar 3, 8:52 am, JOG <j..._at_cs.nott.ac.uk> wrote:
> >>I was hoping perhaps people might be able to offer
> >>perspectives on the issues that they have encountered.
> > Another big difference:
> > Object oriented languages work in object-at-a-time terms.
> > Even when those objects are collections, if one wants to
> > operate on every object in the collection, one iterates
> > over the objects in the collection and calls methods on
> > those objects one at a time.
> > The relational model works in set-at-a-time terms. One
> > operates on entire sets at once.
>
> This is a fallacy.
> In any system, if I have a set S of tuples (x,y) , and request the
> following :
>
> { e IN S : e.x = 123 }
>
> I have to examine each tuple in the set to find those that satisfy the
> predicate. The satisfying tuples do not appear by magic.

Sigh: "magic optimization" (this is indeed a legitimate technical term) is not applied in this case. However, consider an index on column x. Suddenly the execution engine choses an access path more sophisticated than naive loop and application of a filter. The index management and leverage in the queries is completely transparrent from the user. This is one of the features that elevates relational model to high level.

P.S. This de ja vu of the great debate is silly, one of the reason being that the caliber of participants is smaller. Received on Wed Mar 05 2008 - 18:48:33 CET