Re: Object-relational impedence

From: S Perryman <>
Date: Wed, 05 Mar 2008 17:58:30 +0000
Message-ID: <fqmn0b$l6m$>

Tegiri Nenashi wrote:

> On Mar 5, 9:31 am, S Perryman <> wrote:

>>Marshall wrote:

>>>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.

Sigh : in the text "{ e IN S : e.x = 123 }" there is no "index" . Merely a Relational expression.

The use of index is an *implementation* technique.

Argue about implementation techniques as much as you want. But you cannot claim that all OO prog langs will have an implementation that forces the fallacious "one at a time" scheme (Functional programming being a case in point) .

Steven Perryman Received on Wed Mar 05 2008 - 18:58:30 CET

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