如何在查找方法中查询计算字段和条件?

Question

我真的不知道该怎么做。基本上在我的文档中，我有一个比率，我想找到计算比率低于某个值的文档。计算费率如下:

if (rate < 20) {
calculated_rate = rate * 1.25;
} else {
calculated_rate = rate + 5;
}

Answer 1

aggregate(
[
{ 
"$addFields" : { 
"calculated_rate" : { 
"$cond" : [
{ 
"$lt" : [
"$AreasServedRateAndConditions.CGHourlyRate", 
20.0
]
}, 
{ 
"$multiply" : [
"$AreasServedRateAndConditions.CGHourlyRate", 
1.25
]
}, 
{ 
"$add" : [
"$AreasServedRateAndConditions.CGHourlyRate", 
5.0
]
}
]
}
}
}, 
{ 
"$match" : { 
"$and" : [
{ 
"calculated_rate" : { 
"$lte" : 25.0
}
}
]
}
}
], 
{ 
"allowDiskUse" : false
}
);