MongoDb中一个数组中大于某一个数的计数

Question

{
"_id" : ObjectId(""),
"CustomerId" : 13038,
"AT" : ISODate("2021-12-01T04:00:00.000Z"),
"dwell" : [ 
7, 
6, 
12, 
6     ]
},
{
"_id" : ObjectId(""),
"CustomerId" : 12036,
"AT" : ISODate("2021-12-01T04:00:00.000Z"),
"dwell" : [ 
15, 
3, 
12
]
}

在这些文档中，我只想获得驻留中大于10的数字的计数。

例如:

{"CustomerId": 13038, "Count": 1} //because only 12 bigger than 10
{"CustomerId": 12036, "Count": 2}

Answer 1

您可以使用$size和$filter:

db.collection.aggregate([
{
$project: {
_id: 0,
CustomerId: 1,
Count: {
"$size": {
"$filter": {
"input": "$dwell",
"as": "num",
"cond": {
$gt: [
"$$num",
10
]
}
}
}
}
}
}
])

例子MongoPlayground