epg_statistics.rb

# And finally decide EopgStatistics now depends on foo

class EpgStatistics < ActiveRecord::Base
  has_one :foo
  validates_presence_of :foo
end

foo_migration.rb

# After a while you add a new model and migration:

class Foo < ActiveRecord::Base

end

class FooMigration
  self.up 
    create_table :foos |foo|
      # ...
    end
  end
end

migration1.rb

def self.up
  stats = EpgStatistics.all
  change_column :epg_statistics, :lifetime, :float
  change_column :epg_statistics, :latency, :float
  stats.each {|s| s.save}
end