[英]Aggregate in django with duration field
My model is: 我的模型是:
class Mo(Model):
dur = DurationField(default=timedelta(0))
price_per_minute = FloatField(default=0.0)
minutes_int = IntegerField(default=0) # dublicates data from dur , only for test
Some test data: 一些测试数据:
for i in range(4):
m = Mo(dur=timedelta(minutes=i),
minutes_int=i,
price_per_minute=10.0)
m.save()
I want to multiply the dur
by price_per_minute
and find Sum
: 我想通过
price_per_minute
乘以dur
并找到Sum
:
r = Mo.objects.all().aggregate(res=Sum(F('dur')*F('price_per_minute')))
print(r['res']/(10e6 * 60))
but: 但:
Invalid connector for timedelta: *.
Explanation: In database DurationField
is stored as a simple BIGINT that contains micro-seconds, if I know how to obtain it in aggregate I will divide it by (10e6 * 60) and will have paid minutes. 说明:在数据库中,
DurationField
存储为一个包含微秒的简单BIGINT,如果我知道如何以聚合方式获取它,我会将其除以(10e6 * 60)并且将支付分钟数。
If I use a simple IntegerField
instead everything works: 如果我使用一个简单的
IntegerField
代替一切正常:
r = Mo.objects.all().aggregate(res=Sum(F('minutes_int')*F('price_per_minute')))
print(r['res']/(10e6*60))
So I need some cast to integer in the aggregate, is it possible to convert duration to some extra field? 所以我需要在聚合中使用一些转换为整数,是否可以将持续时间转换为一些额外的字段?
r = Mo.objects.all().extra({'mins_int': 'dur'}).aggregate(res=Sum(F('mins_int')*F('price_per_minute')))
print(r['res']),
but 但
Cannot resolve keyword 'mins_int' into field. Choices are: dur, id, minutes_int, price_per_minute
您可以使用ExpressionWrapper(F('dur'), output_field=BigIntegerField())
使Django将dur
视为整数值。
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