From: Eero Saynatkari <ruby-forum-reg@...>
Date: 2005-12-13T07:55:02+09:00
Subject: Re: Hibernate on Ruby

List Recv wrote:
> ActiveRecord is great for small-to-medium things, but does quickly show
> it's limits on large things.  NOTE: Please, do not turn this thread
> into a flame war.  See Martin Fowler's discussion of ActiveRecord
> versus DataMapper.  Rails's ActiveRecord is based on Fowler's
> ActiveRecord pattern, wheras Hibernate is a DataMapper, which Fowler
> himself favors for complicated mappings.
> 
> See DHH's post:
> "No, you don't get the full offer of opportunities that straight OO
> with a data mapper holds. I'd like to think, though, that Active Record
> gives you 80% of the features for 20% of the effort."
> http://www.loudthinking.com/arc/000209.html
> 
> Example for me:
> Let's say I have a class hierarchy, in which a particular field is
> stored direclty in the db for one class, and calculated using a simple
> SQL formula for other other classes.  How can I use the DB to query the
> tree for all objects where field == aVal.
> 
> Answer: In ActiveRecord - you can't (w/o major hacking).  You need to
> instantiate each one from the db, and then use Ruby to check each one.

Google up Og and Kansas and see if either suits you better.
Both take a modeling approach perpendicular to AR. There
are others also, I am sure.

Or, of course, you could restructure your data :)


E

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