在 rails update 中计算 created_at 和 now() 之间的差异

Question

我有一列应该以分钟为单位包含 created_at 和 updated_at 之间的差异，所以我尝试执行以下操作，但它通常将 time_diff 保存为零。那么，我该如何解决呢？

Product.update(
    id,
    time_diff: "((EXTRACT (DAY FROM (now()-created_at))*24*60*60+
                    EXTRACT (HOUR FROM (now()-created_at))*60*60+
                    EXTRACT (MINUTE FROM (now()-created_at))*60+
                    EXTRACT (SECOND FROM (now()-created_at)))/60)::int"
  )

Extract 查询在 SQL 中工作正常，但在 activerecord 的更新中不起作用。

Answer 1

时差的方法很多。您可以自定义时差方法，例如：

def time_diff(start_time, end_time)
  seconds_diff = (start_time - end_time).to_i.abs

  hours = seconds_diff / 3600
  seconds_diff -= hours * 3600

  minutes = seconds_diff / 60
  seconds_diff -= minutes * 60

  seconds = seconds_diff

  "#{hours.to_s.rjust(2, '0')}:#{minutes.to_s.rjust(2, '0')}:#{seconds.to_s.rjust(2, '0')}"
end

并使用它

time_diff(updated_at, created_at) #just example

或者你可以使用 ruby​​ gem time_difference

Answer 2

extract (epoch ...) 给出了一个以秒为单位的间隔，所以使用：

select extract (
    epoch from now() - '2015-09-14 03:06:02.848+02'::timestamp)::int/60 
    as minutes;

 minutes
---------
       7
(1 row)