相等条件在 groupby mongodb 中无法正常工作

Question

相等条件 ($eq) 在 mongo 数据库中无法正常工作。下面是我的 mongo 数据库文档 (table).

{  
"_id":ObjectId("55b08b169d735e293624504a"),
"a":[  
    {  
        "acid":139,
        "akey":"love",
        "atp":"abcd",
        "aadd":" ",
        "adur":3073
    }
],
"created":    ISODate("2015-07-23T06:35:02.959    Z")

}

我的查询是

[  
{  
    "$match":{  
        "created":{  
            "$gte":                ISODate("2015-01-19T07:26:49.045                Z"),
            "$lte":                ISODate("2015-08-20T07:37:56.045                Z")
        }
    }
},
{  
    "$match":{  
        "cid":{  
            $nin:[  
                "59290C6FCCB7E82BD3861F9B6EB46930_2017dec8-0c2c-40c5-9c33-4e3ced0d692f",
                "F098F7DBEFCBAE3ED0E815DE694F2307_8fbe1abc-0d11-443d-bd0a-bf5f181673de",
                "9BAE0D8CA2A3B4BB641C8CCA2A0BD935_d7a76cf4-eb42-41f8-a851-06dd25269fbf"
            ]
        }
    }
},
{  
    "$unwind":"$a"
},
{  
    $group:{  
        _id:"$a.acid",
        "PrestoBarImpression":{  
            "$sum":{  
                "$cond":[  
                    {  
                        "$eq":[  
                            "$a.atp",
                            "abcd"
                        ]
                    },
                    "$total",
                    1
                ]
            }
        },
        "entries":{  
            $sum:1
        }
    }
}

]

我得到以下输出。

{  
"result":[  
    {  
        "_id":139,
        "PrestoBarImpression":0,
        "entries":1.0000000000000000
    }
],
"ok":1.0000000000000000

}

如果我用 ne 而不是 eq，我会得到所需的输出，因为印象数为 1，条目数为 1。

请让我知道我在查询中做错了什么

Answer 1

$eq operator works by comparing two values and returns true when the values are equivalent, false when the values are not equivalent. Thus in your $cond operator, when the $eq operator expression evaluates to true, $cond should return a value of 1 and if the $eq expression evaluates to false then it should return 0 so that the accumulator operator $sum 给出了实际总数。

因此，您的 $group 管道阶段应如下所示：

{  
    $group: {  
        _id: "$a.acid",
        "PrestoBarImpression": {  
            "$sum": {  
                "$cond": [  
                    {  
                        "$eq": [ "$a.atp", "abcd" ]
                    },
                    1,
                    0
                ]
            }
        },
        "entries": { $sum: 1 }
    }
}

相等条件在 groupby mongodb 中无法正常工作

equal condition is not working properly in groupby mongodb

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