mysql execution
alter table thain_flow
add retry_number int unsigned default 0 not null comment '重试次数' after scheduling_status,
add retry_time_interval int unsigned default 0 not null comment '每次重试的间隔,单位秒' after retry_number;
alter table thain_flow_execution
add variables text null comment '执行时赋予的变量' after trigger_type;