本文介绍了使用mongodb聚合的多个字段的不同计数的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
我试图通过一个MongoDB聚合查询来计算多个字段的不同值.
I'm trying to count distinct values of multiple fields By one MongoDB Aggregation query.
这是我的数据:
{
"car_type": "suv",
"color": "red",
"num_doors": 4
},
{
"car_type": "hatchback",
"color": "blue",
"num_doors": 4
},
{
"car_type": "wagon",
"color": "red",
"num_doors": 4
}
我希望每个字段都有不同的计数:
I want a distinct count of each field:
distinct_count_car_type=3
distinct_count_color=2
distinct_count_num_doors=1
我能够对多个字段进行分组,然后进行不同的计数,但是它只能使我对第一个字段计数.不是所有的人.而且这是大量的数据.
I was able to group multiple fields and then do a distinct count but it could only give me a count on the first field. Not all of them.And also it's a large set of data.
推荐答案
您正在寻找... $objectToArray
的力量!
You're looking for the power of ... $objectToArray
!
db.foo.aggregate([
{$project: {x: {$objectToArray: "$$CURRENT"}}}
,{$unwind: "$x"}
,{$match: {"x.k": {$ne: "_id"}}}
,{$group: {_id: "$x.k", y: {$addToSet: "$x.v"}}}
,{$addFields: {size: {"$size":"$y"}} }
]);
这将产生:
{ "_id" : "num_doors", "y" : [ 4 ], "size" : 1 }
{ "_id" : "color", "y" : [ "blue", "red" ], "size" : 2 }
{
"_id" : "car_type",
"y" : [
"wagon",
"hatchback",
"suv"
],
"size" : 3
}
您可以视情况选择$project
或$addFields
包括或排除一组唯一值或大小.
You can $project
or $addFields
as you see fit to include or exclude the set of unique values or the size.
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