mongo中的组,不包括空值

Question

我有mongo查询,它对文档进行组操作.

我几乎得到了预期的结果,除了我想要在没有空值或空值的情况下优化结果.

目前我的查询如下所示:

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 }

如果任何group by字段值为空,或者在DB的实​​际数据中为null,我想删除行.

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 }

Answer 1

您需要一个额外的$match管道步骤,它将根据"$productAttribute.colour"现有的嵌入字段过滤传入的文档,而不是null:

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