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From: "Chris Uppal" <chris.uppal@metagnostic.REMOVE-THIS.org>
Newsgroups: comp.lang.java.programmer
References: <%JGtu.29103$Wm1.26832@fx17.iad> <52b75900$0$9519$9b4e6d93@newsspool1.arcor-online.net>
Subject: Re: ORMs comparisons/complaints.
Date: Fri, 3 Jan 2014 15:38:10 -0000
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Marcel Müller wrote:

> [...quite a bit of interesting stuff...]

Choosing this as a more-or-less arbitrary point to jump in, I have a question.

Given an existing relational database (or set of databases) that:

!) Is/are central to the business (i.e. not there just to "support" some 
specific activity).

2) Is a fairly good relational expression of the underlying business model (but 
see (3) and (7)).

3) Is old, old, old...

4) Is used by more than one application, which are not all written in the same 
language

5) Has severe perfomance problems (caused by the nature of rhe business) even 
when accessed via had-written SQL such that there is a fairly large amount of 
explicit demnormalisation, and the write-measure-rewrite loop is a central part 
of normal, everyday, application development/maintenance. And, even so, many of 
the most important processes take long enough to cause very real operational 
difficulties for customers.

6) Is not simple, in the sense that most of the "entities" that a user would 
think in terms of do not correspond to rows of data in single tables.

7) Has historical quirks (see 3).  Such as: no primary keys (the data has 
primary keys at the logical level, but -- due to history -- the physical DBMS 
itself doesn't know what they are, it just knows about a buch of unique 
indexes).  No FK constraints (again they are there in the logical model, but 
not expressed physically).

Is my feeling that even attempting to use an ORM for developing brand new 
applications against the database would be impossible and/or massively 
counter-productive, actually defensible ?  I.e: am I right to dismiss ORM /out 
of hand/ ?

(Incidentally, of the relatively few database I've come across in 30 years of 
programming, many fit that pattern).

    -- chris