Rails Feeds with SQL View and model: proof of concept

create_feeds.rb

# copied from the texticle gem documentation:
# link: http://tenderlove.github.com/texticle/

class CreateFeeds < ActiveRecord::Migration
  def self.up
    sql = <<-SQL
    CREATE VIEW feeds AS
      SELECT  articles.id AS feedable_id, articles.title AS title,
              CAST ('Article' AS varchar) AS feedable_type 
      FROM articles 
      UNION 
      SELECT  videos.id AS feedable_id, videos.title AS title,
              CAST ('Videos' AS varchar) AS feedable_type 
      FROM videos
    SQL

    execute sql
  end

  def self.down
    sql = "DROP VIEW feeds"
    
    execute sql
  end
end

feed.rb

# copied from the texticle gem documentation:
# link: http://tenderlove.github.com/texticle/

class Feed < ActiveRecord::Base
    
  # We want to reference various models
  belongs_to :feedable, :polymorphic => true
    
  # Feed records are never modified
  def readonly?; true; end

  # Our view doesn't have primary keys, so we need
  # to be explicit about how to tell different
  # results apart; without this, we can't use :include
  # to avoid n + 1 query problems
  def hash
    [feedable_id, feedable_type].hash
  end

  def eql?(result)
    feedable_id == result.feedable_id and
      feedable_type == result.feedable_type
  end
  
end