Question

我有如下嵌套数据，

db.fbresults.aggregate([{$match:{academicyear:"2017-18",fdept:'Comp'}},{$group:{_id: {fname: "$fname", rating:"$fbValueList.rating"},count: {"$sum":1}}}])

我们正尝试使用此功能执行聚合，

{ "_id" : { "fname" : "ABC", "rating" : [ "Fair","Fair","Excellent","Very Good", "Very Good",  "Excellent", "Good", "Good" ] }, "count" : 2 }

我们得到的结果如，

{ "_id" : { "fname" : "ABC", "rating_group" : [ 
        { 
            rating: "Excellent"
            count: 2 
        },
            { 
            rating: "Very Good"
            count: 2 
        },
            { 
            rating: "Good"
            count: 2 
        },
            { 
            rating: "Fair"
            count: 2 
        },

    ] }, "count" : 2 }

但是我们期待像

这样的结果

numbers.sum

numbers.inject(:+)

我们希望通过他们的名字和他们的评级反应和评级数量来获得个人教师团体。

我们已经尝试过这个但我们没有结果。 Mongodb Aggregate Nested Group

Answer 1

这应该让你前进：

db.collection.aggregate([{
    $match: {
        academicyear: "2017-18",
        fdept:'Comp'
    }
}, {
    $unwind: "$fbValueList" // flatten the fbValueList array into multiple documents
}, {
    $group: {
        _id: {
            fname: "$fname",
            rating:"$fbValueList.rating"
        },
        count: {
            "$sum": 1 // this will give us the count per combination of fname and fbValueList.rating
        }
    }
}, {
    $group: {
        _id: "$_id.fname", // we only want one bucket per fname
        rating_group: {
            $push: { // we push the exact structure you were asking for
                rating: "$_id.rating",
                count: "$count"
            }
        },
        count: {
            $avg: "$count" // this will be the average across all entries in the fname bucket
        }
    }
}])

Answer 2

这是一个长聚合管道，可能会有一些不必要的聚合，所以请检查并丢弃哪些不相关。

注意：这只适用于Mongo 3.4+。

您需要使用$unwind，然后使用$group和$push评分及其计数。

matchAcademicYear = {
    $match: { 
        academicyear:"2017-18", fdept:'Comp' 
    }
}

groupByNameAndRating = {
    $group: {
        _id: { 
            fname: "$fname", rating:"$fbValueList.rating"
        },
        count: {
            "$sum":1
        }
    }
}

unwindRating = {
    $unwind: "$_id.rating"
}

addFullRating = {
    $addFields: {
        "_id.full_rating": "$count"
    }
}

replaceIdRoot = {
    $replaceRoot: {
        newRoot: "$_id"
    }
}


groupByRatingAndFname = {
    $group: {
        _id: {
            "rating": "$rating",
            "fname": "$fname"
        },
        count: {"$sum": 1},
        full_rating: {"$first": "$full_rating"}
    }
}

addFullRatingAndCount = {
    $addFields: {
        "_id.count": "$count",
        "_id.full_rating": "$full_count"
    }
}

groupByFname = {
    $group: {
        _id: "$fname",
        rating_group: { $push: {rating: "$rating", count: "$count"}},
        count: { $first: "$full_rating"}
    }    
}

db.fbresults.aggregate([
    matchAcademicYear, 
    groupByNameAndRating, 
    unwindRating, 
    addFullRating, 
    unwindRating, 
    replaceIdRoot, 
    groupByRatingAndFname, 
    addFullRatingAndCount, 
    replaceIdRoot, 
    groupByFname
])

MongoDB聚合嵌套数据

2 个答案: