def rename_column(old, nu)
      col = @origin.columns[old.to_s]

      definition = col[:type]
      definition += ' NOT NULL' unless col[:is_nullable]
      definition += " DEFAULT #{@connection.quote(col[:column_default])}" if col[:column_default]

      ddl('alter table `%s` change column `%s` `%s` %s' % [@name, old, nu, definition])
      @renames[old.to_s] = nu.to_s
    end
def rename_column(old, nu)
      col = @origin.columns[old.to_s]

      definition = col[:type]
      definition += ' NOT NULL' unless col[:is_nullable]
      definition += " DEFAULT #{@connection.quote(col[:column_default])}" if col[:column_default]

      ddl('alter table `%s` change column `%s` `%s` %s' % [@name, old, nu, definition])
      @renames[old.to_s] = nu.to_s
    end
Rename an existing column.

 @example

   Lhm.change_table(:users) do |m|
     m.rename_column(:login, :username)
   end

 @param [String] old Name of the column to change
 @param [String] nu New name to use for the column