instance method add_index_options

# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 532
        def add_index_options(table_name, column_name, options = {})
          column_names = Array.wrap(column_name)
          index_name   = index_name(table_name, :column => column_names)

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

          if index_name.length > index_name_length
            raise ArgumentError, "Index name '#{index_name}' on table '#{table_name}' is too long; the limit is #{index_name_length} characters"
          end
          if index_name_exists?(table_name, index_name, false)
            raise ArgumentError, "Index name '#{index_name}' on table '#{table_name}' already exists"
          end
          index_columns = quoted_columns_for_index(column_names, options).join(", ")

          [index_name, index_type, index_columns]
        end