in lib/tasks

populate.rake

namespace :db do
  desc "Erase and fill database"
  task :populate => :environment do
    require 'populator'
    #require 'faker'

    [Category, Record].each(&:delete_all)

    Category.populate 10 do |category|
      category.title = Populator.words(2)
      Record.populate 500..1000 do |record|
        record.title = Populator.words(3)
        record.amount = 10..10000        
        record.category_id = category.id
        record.date = Date.new(2012,2,3)...Date.new(2012,12,30)
      end
    end
  end
end