# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 166
      def add_index(table_name, column_name, options = {})
        index_name = "#{table_name}_#{Array(column_name).first}_index"

        if Hash === options # legacy support, since this param was a string
          index_type = options[:unique] ? "UNIQUE" : ""
          index_name = options[:name] || index_name
        else
          index_type = options
        end

        execute "CREATE #{index_type} INDEX #{index_name} ON #{table_name} (#{Array(column_name).join(", ")})"
      end