add_index

# File activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb, line 444
        def add_index(table_name, column_name, **options) #:nodoc:
          index, algorithm, if_not_exists = add_index_options(table_name, column_name, **options)

          create_index = CreateIndexDefinition.new(index, algorithm, if_not_exists)
          result = execute schema_creation.accept(create_index)

          execute "COMMENT ON INDEX #{quote_column_name(index.name)} IS #{quote(index.comment)}" if index.comment
          result
        end