如何在mongoDB中获取多个匹配过滤器计数 [英] How to get multi matching filters count in mongoDB

问题描述

我收集了大约50000个文档.集合模式如下:

I have around 50000 documents in collection. Collections Schema looks like this:

{ param1: Boolean, param2: Boolean, param3: Boolean, param4: Boolean } //etc

我应该如何查询数据库，以获取每个匹配的参数计数. 目前，我正在循环调用每个参数:

How should i make query to db, to get each matching param count. Currently, I'm calling each param in a loop:

db.getCollection('patients').count({ param1: true } )
db.getCollection('patients').count({ param2: true } )
db.getCollection('patients').count({ param3: true } ) ...

我觉得这是不正确的方法，请给我一些建议，如何在一个查询中获取此信息.

I feel, this isn't right way, please give me some advise, how to get this information in one query.

推荐答案

通过 聚合框架 .

Very possible in one go via the aggregation framework.

在MongoDb 3.6和更高版本中，您可以利用 $arrayToObject 运算符> $replaceRoot 管道即可获得所需的结果.

With MongoDb 3.6 and newer, you can leverage the use of $arrayToObject operator within a $replaceRoot pipeline to get the desired result.

在管道中，利用

Within the pipeline, take advantage of the $cond operator in the $group stage to evaluate the counts based on the param field boolean value, something like the following:

db.getCollection('patients').aggregate([ 
    { "$project": { "_id": 0 } },
    { "$project": { "data": { "$objectToArray": "$$ROOT" } } },
    { "$unwind": "$data" },
    { "$group": { 
        "_id": "$data.k", 
        "count": { 
            "$sum": {
                "$cond": [ "$data.v", 1, 0 ] 
            }
        } 
    } },
    { "$group": { 
        "_id": null, 
        "counts": { 
            "$push": { "k": "$_id", "v": "$count" } 
        } 
    } }, 
    { "$project": { 
        "data": { "$arrayToObject": "$counts" } 
    } }, 
    { "$replaceRoot": { "newRoot": "$data" } } 
])

---

对于不支持上述 的MongoDB版本$arrayToObject 和 运算符，则在计算总和时需要在组管道中明确指定字段:

---

For MongoDB versions that do not have support for the above $arrayToObject and $replaceRoot operators, you would need to explicitly specify the fields in the group pipeline when calculating the sums:

db.getCollection('patients').aggregate([    
    { "$group": { 
        "_id": null,             
        "param1_count": {
            "$sum": {
                "$cond": [ "$param1", 1, 0 ] /* similar to "$cond": [ { "$eq": [ "$param1", true ] }, 1, 0 ] */
            }
        },
        "param2_count": {
            "$sum": {
                "$cond": [ "$param2", 1, 0 ]
            }
        },
        "param3_count": {
            "$sum": {
                "$cond": [ "$param3", 1, 0 ]
            }
        },
        "param4_count": {
            "$sum": {
                "$cond": [ "$param4", 1, 0 ]
            }
        } 
    } },
    { "$project": {
        "_id": 0,             
        "param_counts": {
            "param1": "$param1_count",
            "param2": "$param2_count",
            "param3": "$param3_count",
            "param4": "$param4_count"
        }
    } }
])

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