Newsgroups: comp.lang.smalltalk
From: Andy@kahuna.demon.co.uk (Andy Deighton)
Path: cantaloupe.srv.cs.cmu.edu!das-news2.harvard.edu!news2.near.net!MathWorks.Com!europa.eng.gtefsd.com!howland.reston.ans.net!pipex!demon!kahuna.demon.co.uk!Andy
Subject: Re: Persistent objects in RDBMS
References: <35b7om$9s7@panix.com> <35cmhc$rc@ams.amsinc.com> <35ga59$idf@panix.com> <CxGnIL.2ns@heeg.de>
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Date: Fri, 14 Oct 1994 22:05:43 +0000
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In article <CxGnIL.2ns@heeg.de> hasko@heeg.de "Hasko Heinecke" writes:

> In article <35ga59$idf@panix.com> dsiegel@panix.com (David Siegel) writes:
> >In <35cmhc$rc@ams.amsinc.com> mark_murphy@mail.amsinc.com (Mark Murphy) writes:> >
> >>If DataLens, et. al. are not what you are looking for, I will be somewhat
> >>surprised to hear of anything else closer that uses an RDBMS.
> >
> >Why?  It's clear that you can be more ambitious than the current version
> >of DataLens -- ParcPlace's own documentation alludes to future enhancements.
> >In particular, it should be possible to preserve polymorphic instance
> >variables at the cost of not being able to retrieve data via simple joins.
> >
> >>If you are expecting an array of truly arbitrary objects
> >>to be stored in a single table (like, say, BOSS can write to a file), you may
>  be
> >>disappointed.
> >
> >I'd expect each class to have a separate table, but I'd expect an instance
> >variable to reference an object in one of many tables.
> 
> You'd need another table for every single object with a variable number of
> inst vars, like Collections.
> 
> Hasko
> -- 
> +-------------------------------------------------------+
> | Hasko Heinecke speaking for myself only               |
> | I _never_ mean what I say - and nobody else does...   |
> +-------------------------------------------------------+
> 
For an idea of what a *good* object->RDBMS mapper should do, 
try looking at the new release of Easel's Synchronicity (version 2) tool, 
that now includes a Persistent Object Mapping Tool.  This allows ENFIN 
Smalltalk objects to be saved, updated, retrieved, deleted in an RDBMS.
It creates the necessary SQL, and handles concurrency, allowing the 
developer to simply think in terms of objects rather than rows and columns. 
This goes way beyond the datalens technology in VW2.  
Relational issues (an instance of class SalesOrder relates to one or more 
LineItem objects) including many-to-many are handled automatically.  
You should really take a look at it.  Easel (US) are on 617 221 2100.
-- 
Andy J. Deighton
<-=-=-=-=-=-=-=>
