mongo中的组，不包括空值 [英] group in mongo excluding null values

问题描述

我有mongo查询，可以对文档进行分组操作.

I have mongo query which does the group operation on the documents.

除了要优化结果而没有空值或空值之外，我几乎得到了预期的结果.

I have almost got the expected results except that I want to refine the results without empty or null values.

当前我的查询如下:

db.productMetadata.aggregate([{$group:{"_id":{"color":"$productAttribute.colour","gender":"$productAttribute.gender"},"count" : {$sum : 1}}}]);

结果看起来像这样:

{ "_id" : { "color" : "BLUE", "gender" : "MEN" }, "count" : 1 }
{ "_id" : {  }, "count" : 4 }
{ "_id" : { "color" : "NA", "gender" : "WOMEN" }, "count" : 1 }
{ "_id" : { "color" : "BLACK", "gender" : "MEN" }, "count" : 1 }
{ "_id" : { "color" : "BROWN", "gender" : "WOMEN" }, "count" : 1 }
{ "_id" : { "gender" : "MEN" }, "count" : 2 }
{ "_id" : { "color" : "BEIGE", "gender" : "MEN" }, "count" : 1 }
{ "_id" : { "color" : "BROWN", "gender" : "MEN" }, "count" : 1 }

如果数据库的实际数据中的group by字段值中的任何一个为空或为null，我想删除这些行.

I want to remove the rows if any of the group by field values are empty or null in the actual data of DB.

例外结果应如下所示:

{ "_id" : { "color" : "BLUE", "gender" : "MEN" }, "count" : 1 }
{ "_id" : { "color" : "NA", "gender" : "WOMEN" }, "count" : 1 }
{ "_id" : { "color" : "BLACK", "gender" : "MEN" }, "count" : 1 }
{ "_id" : { "color" : "BROWN", "gender" : "WOMEN" }, "count" : 1 }
{ "_id" : { "color" : "BEIGE", "gender" : "MEN" }, "count" : 1 }
{ "_id" : { "color" : "BROWN", "gender" : "MEN" }, "count" : 1 }

推荐答案

您需要额外的 $match 管道步骤，该步骤将基于存在的嵌入式字段"$productAttribute.colour"而不是null来过滤传入的文档:

You need an extra $match pipeline step that will filter the incoming documents based on the embedded field "$productAttribute.colour" existing and not null:

    db.productMetadata.aggregate([
    { 
        "$match": {
            "productAttribute.colour": { 
                "$exists": true, 
                "$ne": null 
            }
        }    
    },
    { 
        "$group": {
            "_id": {
                "color": "$productAttribute.colour",
                "gender": "$productAttribute.gender"
            },
            "count": { 
                "$sum": 1 
            }
        }   
    }        
]);

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