I’m a big fan of the yaml_db plugin. But I don’t like running rake db:data:load, only to find that my db columns mismatch my model attributes, thus aborting the data import task. To quickly add/remove columns/attributes from a model and rebuild the database with previous db info, I wrote this simple rake task. It saves model records as yaml in db/seandb.yml, and reloads them in the same task but with the db rebuilt. I nest the save method in begin/rescue so that if there are any conflicts the task will continue.

This biggest challenge was to get a list of all the active record models in the Rails app. This problem has been posted a lot and I didn’t find an easy solution. For now, I just look in the app/models directory and ‘classify’ and ‘constantize’ the file name. This will load the model so that I can iterate over all the active record subclasses and call the appropriate Model.find(:all) method. I could maybe do the same w/ all files in the Rails.configuration.load_paths, but my models are, at least for now, under app/models. Plugin models are loaded and available from the rake task if you require the :environment.

It’s as simple as running

rake db:everything

SAVEDB = "#{RAILS_ROOT}/db/seandb.yml"
namespace :db do
   task :everything => [:environment, :spit, :drop, :create, :migrate, :populate] do
     desc "spit out model records as yaml, rebuild the database and repopulate the db"
   end

   task :spit do
    Dir["#{RAILS_ROOT}/app/models/*"].each {|file| (File.basename(file,".*").classify.constantize)}
    File.open(SAVEDB, "w") do |f|
      ActiveRecord::Base.send(:subclasses).each do |model|
        begin
          model.find(:all).each do |record|
              f.write(record.to_yaml)
              print "\twrote #{record.class}\n"
          end
        rescue
        end
      end
    end
   end

   task :populate do
    File.open( SAVEDB ) do |yf|
      YAML.each_document( yf ) do |ydoc|
        begin
          m = ydoc.clone
          m.save
          p "...saved #{m.id}"
        rescue
        end
      end
    end
   end
end

Get the plugin like so…

script/plugin install git://github.com/adamwiggins/yaml_db.git

This command will dump your data

rake db:data:dump

And load it back

rake db:data:load

Beautiful :) More info here

http://blog.heroku.com/archives/2007/11/23/yamldb_for_databaseindependent_data_dumps/

and

http://stackoverflow.com/questions/490507/best-way-to-export-a-database-table-to-a-yaml-file