On 2/2/08 3:56 PM, "Ilan Berci" <coder68 / yahoo.com> wrote:

> Softmind Technology wrote:
>> Hello,
>> 
>> Comparing Active Record VS DataMapper...?
>> 
>> Can any one provide more details on this..
>> 
>> Any Links of Blogs comparing the above two.
>> 
>> I shall also welcome your suggestions on this.
>> 
>> Thanks
> 
> I was curious about this myself, I have used AR for years now and I was
> interested in DM's promise of no migrations and optional lazy loading of
> fields.  I have no problem expressing my fields in the models (I
> actually like it) and I have no problem being committed to MySQL. If DM
> can update your schema automagically when seeing an
> incompatibility/update with your model then I won't sleep for a week due
> to the magic of it all.
> 
> I used to think that migrations were the best thing since sliced bread
> but due to the fact that AR attempts to cater to every major vendor, I
> usually  have to go in a hand tune my migrations anyways (bigint and
> foreign key constraints which I realize many feel are unnecessary when
> working with RoR).  I also used to follow OG as well but after some
> playing around, i came to the conclusion that updating the schema with
> it was far more difficult than it was with AR.
> 
> Merb right now is a big carrot for me and it has direct support (through
> gem dloads) for haml AND DataMapper so I think something truly great (or
> at least very exciting) is in the mix!  Due to the fact that I am a
> coward however, I still use AR at work as I am very comfortable with it
> and I finally got used to a lot of it's black magic through
> method_missing craziness.
> 
> Merb/DataMapper is a cinch to dload and set up so you should see it for
> yourself..
> ilan
> 
> 
I'm no DM expert, but from my perspective the benefits are:

- Really modular: Add-ons installed as gems (AR is kind of moving this way)
- Thread safe. 'Nuff said.
- Works in Rails, Merb, and stand-alone Ruby programs

Now the magic migrations (ala Og) have been a subject of some debate because
They toast the table when they happen. As I understand it, adding a country
field to an address table would drop the table and recreate it. This can be
a particularly annoying side effect when dealing with tables that have
related tables, or worse, habtm.

There are claims that DM is faster than AR, but I have yet to demonstrate
that on any of my sample data. They seem pretty much on a par.

Download it and stick it in one of your play apps to see what happens.