MongoDB Aggregate $group 用于两个累积字段

Question

我有以下文件

{ 
   id: ObjectId,
   branch: ObjectId,
   name: "lorem ipsum",
   type: "Delivery",
   total: 10.5
},
{ 
   id: ObjectId,
   branch: ObjectId,
   name: "lorem ipsum 22",
   type: "Carry out",
   total: 7.5
}, 
.
.
.

我正在尝试计算每个订单type
每个分支的平均total 像这样的每个分支的预期结果

{
   branch: ObjectId,
   name: "lorem ipsum",
   deliveryAVG: 8.7,
   CarryOut: 6.9
}

有什么建议吗？

Answer 1

您可以使用$group 两次按分支和类型聚合，然后使用$arrayToObject 将每种类型转换为新的对象键：

db.collection.aggregate([
    {
        $group: {
            _id: {
                branch: "$branch",
                type: "$type"
            },
            avg: { $avg: "$total" },
            name: { $first: "$name" }
        }
    },
    {
        $group: {
            _id: "$_id.branch",
            name: { $first: "$name" },
            averages: {
                $push: {
                    k: "$_id.type",
                    v: "$avg"
                }
            }
        }
    },
    {
        $replaceRoot: {
            newRoot: {
                $arrayToObject: {
                    $concatArrays: [ "$averages", [ { "k": "_id", "v": "$_id" }, { "k": "name", "v": "$name" } ] ]
                }
            }
        }
    }
])

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