python - Django + MySQL : Round Robin Update of Same Table Columns

Question

我的模型有点像

Spot 
    spot_1 = 1/0
    spot_2 = 1/0
    spot_3 = 1/0
    spot_4 = 1/0
    spot_5 = 1/0
    spot_6 = 1/0

有点像 Round Robin Database，假设 spot_1 代表当前月份，spot_2 代表上个月，依此类推。所以如果当前月份是六月，那么

Jun  = spot_1  
May  = spot_2  
Apr  = spot_3  
Mar  = spot_4  
Feb  = spot_5  
Jan  = spot_6  

所以在 6 月底和 7 月初，这将表示为

July = spot_1  
Jun  = spot_2  
May  = spot_3  
Apr  = spot_4  
Mar  = spot_5  
Feb  = spot_6  

所以值(value)观也应该发扬光大。目前我正在遍历整个 QuerySet 并使值向前移动。

这如何通过单个 update() 语句实现？

Answer 1

使用 F表达式:

from django.db.models import F

Spot.objects.all().update(spot_2=F('spot_1'), spot_3=F('spot_2'), ...)