查询语句：
db.collection('taskToUser').aggregate()
.unwind('$userList')
.group({
_id: '$userList.userId',
sum: $.sum(1),
sumTrue: $.sum(1),
sumFalse: $.sum(1),
})
.end()
查询结果：
[
{
"_id": "ovXd05X4Dep9Z6Y2siKO1YKZOd8E",
"sum": 27,
"sumTrue": 27,
"sumFalse": 27
},
{
"_id": "ovXd05RxUd-W39WyGbAdca7XwKfE",
"sum": 27,
"sumTrue": 27,
"sumFalse": 27
},
{
"_id": "ovXd05WQOtTLR_IPYs6_UTq2NNDE",
"sum": 91,
"sumTrue": 91,
"sumFalse": 91
}
]
我想让sum1字段和sum2字段，根据数据的一个字段（bool类型的）来判断是否计数，结果类似这样：sum=sumTrue+sumFalse
{
"_id": "ovXd05WQOtTLR_IPYs6_UTq2NNDE",
"sum": 91,
"sumTrue": 40,
"sumFalse": 51
}
刚看了下sum的参数是Expression表达式，所以写出来了，不知道还有没有更简便的方法
db.collection('taskToUser').aggregate() .unwind('$userList') .group({ _id: '$userList.userId', sum: $.sum(1), sumTrue: $.sum( $.cond({ if: $.eq(['$userList.isCompeted', true]), then: 1, else: 0 }) ), sumFalse: $.sum( $.cond({ if: $.eq(['$userList.isCompeted', false]), then: 1, else: 0 }) ), }) .sort({ sumTrue: -1 }) .end()