change_column_for_alter

# File activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb, line 730
          def change_column_for_alter(table_name, column_name, type, **options)
            td = create_table_definition(table_name)
            cd = td.new_column_definition(column_name, type, **options)
            sqls = [schema_creation.accept(ChangeColumnDefinition.new(cd, column_name))]
            sqls << Proc.new { change_column_comment(table_name, column_name, options[:comment]) } if options.key?(:comment)
            sqls
          end