# File lib/active_record/connection_adapters/postgresql_adapter.rb, line 674
      def columns(table_name, name = nil)
        # Limit, precision, and scale are all handled by the superclass.
        column_definitions(table_name).collect do |name, type, default, notnull|
          PostgreSQLColumn.new(name, default, type, notnull == 'f')
        end
      end