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Subject: Re: Generic Package
From: Georg Bauhaus <bauhaus@futureapps.de>
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Date: Fri, 27 Apr 2007 16:10:47 +0200
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Date: 2007-04-27T16:05:08+02:00
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On Fri, 2007-04-27 at 14:06 +0200, Dmitry A. Kazakov wrote:

> > Any real table in an existing computer has a "natural"
> > ordering suitable for iterating an operation for all
> > elements: data in a real computer can be uniquely identified.
> 
> No this is wrong even on a real computer. The DB engine could shuffle the
> rows asynchronously to your application.

So what? Any delivery of DB rows to an application
permits iteration as long as Iterate knows how to
create a sequence from the inputs. I can't think of
a DB system, in particular in the OP's context, that
will deliver rows such that the recipients must be able
to perform processing of more than one row at the same tick.


> > The fact that the ordering is hidden behind the functional
> > Iterate abstraction doesn't make it go away for any
> > snapshot of rows.
> 
> It does. Semantically, table /= a snapshot of. That is.

For Iterate, a snapshot is a table, a collection of tuples.
Semantically, every DB client program I have ever seen is
based on the very fact that a snapshot is a table.