oldhaven/lib/tasks/db_cleanup.rake

namespace :db do
  desc 'Cleans artist-album-track relations clean'
  task :cleanup => :environment do
    
    albums = Album.all
    albums.each do |album|
      if album.artist.nil?
        album.delete
      end
    end
    
    tracks = Track.all
    tracks.each do |track|
      if track.album.nil?
        track.delete
      end
    end
    
  end
end