From: Ryan Glover <prionscientific@...>
Date: 2006-12-28T10:19:29+09:00
Subject: Re: Modified Single Table Inheritance

Hello David,

> Why are they deriving from a single class anyway?

All the objects are the same thing, so to speak.  As a silly example of 
what I am trying to do, let's say that each user an array named fruit. 
There are many types of fruit and each have their own unique attributes 
(# of grapes, fuzziness index of peach, banana radius) but they are all 
fruit.  My program is just like this, except I have hundreds of fruit. 
Perhaps even a thousand.  Ideally I would like to be able to add more 
fruit as the program evolves just by adding a new fruit subclass and a 
new fruit view.

> 
> I can't understand this. It's rather common that an ORM database schema
> has a number of tables in the same order of magnitude as there are model
> classes. My biased opinion is that data should be modelled on the
> database level where you have some theorethical foundations about what
> are "good shapes" for the data. It also doesn't hurt to at least make
> the DB schema somewhat document the data model - the data an application
> gathers / stores is the most likely part of it to persist in the long
> term. Of course, you're probably in a better position to judge this.
> 

I guess my problem with 100's perhaps a 1000 tables is db performance. 
I don't have oracle, only mysql or postgres.  Performance wise, wouldnt 
it be better to have a few thousand rows in one table as opposed to a 
few dozen spread across 100's of tables?


> Database schemas like this tend to make it into The Daily WTF with some
> regularity.
> 
> (Unfortunately, they also make it into production systems.)
> 
> If there's a chance someday, someone, somewhy might want to access your
> data at a DB level (using a reporting tool maybe), there'd be no end to
> the grief.
> 
> Or, if a bug in your code gets the database into an inconsistent state,
> and you have to drop down to SQL to patch things up.
> 
> Avoid.

I appreciate all these warnings and I understand what you are saying. 
In this case I am client for the project so I'll take my lumps as they 
come.

Thanks for your response,
Ryan Glover



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