Mongodb mongo中的组，不包括空值

我有mongo query，它对文档执行组操作

我几乎得到了预期的结果，除了我想在没有空值或空值的情况下优化结果

当前我的查询如下所示：

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

{ "_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 }

{ "_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 }

结果如下所示：

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

{ "_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 }

{ "_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 }

如果GROUPBY字段值在DB的实际数据中为空或null，我想删除这些行

例外结果应如下所示：

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

{ "_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 }

{ "_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 }

---

您需要一个额外的管道步骤，该步骤将根据嵌入字段

“$productAttribute.color”

现有且不为空来过滤传入文档：

db.productMetadata.aggregate([
{ 
“$match”：{
“productAttribute.Color”：{
“$exists”：正确，
“$ne”：空
}
}    
},
{ 
“$group”：{
“_id”：{
“颜色”：“$productAttribute.color”，
“性别”：“$productAttribute.gender”
},
“计数”：{
“$sum”：1
}
}   
}        
]);

也许您应该在$group操作之前使用$match:{'color'：{$exists:true}}。使用稀疏索引，它将运行得非常快。

---

并且不要在集合中存储“null”字段，这将减少数据库大小并提高索引搜索速度（索引中的文档越少->速度越快）

此示例包括两个不同的集合。为此，我们使用聚合函数。我也在使用猫鼬

我将加入cusmtomfield和customfiellabels，使用$lookup

使用$REWIND展开阵列

$match以排除文本中不活动的名称（我使用的是REGEX）

$project重命名字段以在客户端上正确显示

。 异步getAllMasterDataCustomFields（req）{

谢谢，我一直在到处寻找这个。这是否意味着$match是唯一可以与查询运算符一起使用的聚合阶段？查询运算符实际上是什么？