lib/arjdbc/teradata/adapter.rb
def change_column(table_name, column_name, type, options = {}) #:nodoc:
      change_column_sql = "ALTER TABLE #{quote_table_name(table_name)} " <<
          "ADD #{quote_column_name(column_name)} #{type_to_sql(type, options[:limit])}"
      add_column_options!(change_column_sql, options)
      execute(change_column_sql)
    end
def change_column(table_name, column_name, type, options = {}) #:nodoc:
      change_column_sql = "ALTER TABLE #{quote_table_name(table_name)} " <<
          "ADD #{quote_column_name(column_name)} #{type_to_sql(type, options[:limit])}"
      add_column_options!(change_column_sql, options)
      execute(change_column_sql)
    end
+ change_column
 This only works in a VERY limited fashion.  For example, VARCHAR columns
 cannot be shortened, one column type cannot be converted to another.