$ replaceRoot在mongodb中

本文介绍了$ replaceRoot在mongodb中的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！

问题描述

我将聚合框架用于多个字段的分组依据

I use aggregation framework for group by of multiple fields as

{
_id:{_id:"$_id",feature_type:"$feature_type",feature_name:"$feature_name"},
features: { $push: "$features" }
}

给出类似

{_id:
     {_id:1,feature_type:"Test",feature_name:"Tests"},
  features:["23423","32423","2342342"]
}

但是我想要类似

{_id:1,feature_type:"Test",feature_name:"Tests",
  features:["23423","32423","2342342"]
}

我如何使用聚集框架来实现这一目标.

how can i acheve this using aggregration framework.

推荐答案

db.collection.aggregate([
  {      
      $project: {
                _id: "$_id._id",
                feature_type:"$_id.feature_type",
                feature_name:"$_id.feature_name",
                features:1
                }
  }
])

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