quoted_columns_for_index

# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 1470
      def quoted_columns_for_index(column_names, options) # :nodoc:
        quoted_columns = column_names.each_with_object({}) do |name, result|
          result[name.to_sym] = quote_column_name(name).dup
        end
        add_options_for_index_columns(quoted_columns, **options).values.join(", ")
      end