CQRS in a Rails environment?

I'm trying to wrap my head around CQRS (Command Query Response Separation) per Martin Fowlers recent post at:

http://martinfowler.com/bliki/CQRS.html

Given开发者_JAVA百科 a project:

Main Database (Postgres):
  Product has many Sales
  User has many Sales

Reporting Database (NoSQL - Mongodb)
  Transaction (A Product and a Sale and a User)

And a requirement of producing a chart of transaction dollars per day for a given month.

• What controllers would I need for reporting?
  • A Reports controller for views and partials
  • A Graphs controller for pulling the specific info for a graph out of the Reporting DB?
• What the heck would the DTO (Data-Transfer Object) be in this case?
• Is this really CQRS?
  • I assume so, since Reports/Graphs created from reporting DB would not be changing state, just a view on the main DB?

Thanks!

If you're still interested in investigating CQRS with Rails have a look at rcqrs a Ruby CQRS with Event Sourcing library I created.

There's also a Rails 3 plugin to integrate with your Rails app that comes with generators to ease common tasks for creating commands, events and controllers using the CQRS pattern.

Finally, there is a very simple sample blog Rails application to look at how you might use CQRS with Rails (look at my GitHub account for more details).

I guess you need read more about CQRS first, before try apply it. Because of CQRS is not Command Query Response Separation but Command and Query Responsibility Segregation.

I suggest to start reading from Greg Yuong cqrs info and any articles about cqrs by Udi Dahan and Martin Fowler as well. And after that take a look on exists implementations of cqrs.

With cqrs you usually will have two databases: Read and Write. Write database is usually normalized store. Read database -- database that will contains data in denormalized form to minimize the number of joins needed to get a given set of data.