class ActiveRecord::ConnectionAdapters::ReferenceDefinition

def add(table_name, connection)
  columns.each do |name, type, options|
    connection.add_column(table_name, name, type, **options)
  end
  if index
    connection.add_index(table_name, column_names, **index_options(table_name))
  end
  if foreign_key
    connection.add_foreign_key(table_name, foreign_table_name, **foreign_key_options)
  end
end