MongoDB 分组

Question

我有mongoDBcollection这样

{ 
    "_id" : "EkKTRrpH4FY9AuRLj",
    "stage" : 10,
},
{ 
    "_id" : "EkKTRrpH4FY9AuRLj",
    "stage" : 10,
},
{ 
    "_id" : "EkKTRrpH4FY9AuRLj",
    "stage" : 20,
}

我想把它分组在

stage: 10 in paid 
stage: 20 in unpaid

结果应该是这样的

{
    "paid": [
        { 
            "_id" : "EkKTRrpH4FY9AuRLj",
            "stage" : 10,
        },
        { 
            "_id" : "EkKTRrpH4FY9AuRLj",
            "stage" : 10,
        }
    ],
    "unpaid": [
        { 
            "_id" : "EkKTRrpH4FY9AuRLj",
            "stage" : 20,
        }
    ]
}

我该怎么做？

Answer 1

建议使用 aggregation framework for this where you'd need to run an initial $group staged pipeline that uses the operators $push to create the new arrays, and $cond 评估某些条件并使用逻辑嵌入正确的文档。

最终的 $project pipeline step is necessary to prune some of the array elements from the previous pipeline that are redundant, i.e. filter out the [false] values by using the $setDifference 运算符。

考虑运行以下显示 mongo shell 中的聚合管道：

db.collection.aggregate([
    {
        "$group": {
            "_id": null,
            "paid": {
                "$push": {
                    "$cond": [ 
                        { "$eq": [ "$stage", 10 ] }, 
                        { "_id": "$_id", "stage": "$stage" }, 
                        false
                    ]
                }
            },
            "unpaid": {
                "$push": {
                    "$cond": [ 
                        { "$eq": [ "$stage", 20 ] }, 
                        { "_id": "$_id", "stage": "$stage" }, 
                        false
                    ]
                }
            }
        }
    },
    {
        "$project": {
            "_id": 0,
            "paid": {
                "$setDifference": [ "$paid", [false] ]
            },
            "unpaid": {
                "$setDifference": [ "$unpaid", [false] ]
            }
        }
    }
])

在 Mongo.Collection 个实例上添加 meteorhacks:aggregate package that exposes .aggregate() 方法。请注意，这仅适用于服务器端，并且没有内置的观察支持或反应性。

使用

添加到您的应用

meteor add meteorhacks:aggregate

MongoDB 分组

MongoDB GroupBy

mongodb

angular-meteor