ALTER TABLE lhm migration deletes existing values

require 'lhm'

class RenameField1ToField2ForTable < ActiveRecord::Migration
  def up
    Lhm.change_table :table do |m|
      m.ddl("ALTER TABLE %s CHANGE COLUMN field1 field2 FLOAT DEFAULT NULL AFTER field3" m.name)
    end
  end

  def down
    Lhm.change_table :table do |m|
      m.ddl("ALTER TABLE %s CHANGE COLUMN field2 field1 FLOAT DEFAULT NULL AFTER field3" m.name)
    end
  end
end

What happend:

1. Rails-4.0: rake db:migrate
2. Field was renamed successfully.
3. All existing field values are erased, why? Any ideas?

Edit:

• old datatype was float(11)
• MYSQL 5.6