Remove _id after grouping stage in aggregation

[Mukul Sharma]

Version : 2.6.1

I'm using the group aggregation in mongodb, & writing the result to a collection using $out.

Is there way to prevent the _id field in aggregation result from going into the newly created collection.

One way using the $project stage, & removing _id & including the others.

Is there a better or neat way of doing this ?

[Stephen Steneker]

Hi Makul,

An _id field is required for the $group operation. If you want to remove the _id field after grouping, an extra $project would be the best way to do so.

Regards,

Stephen 

[Asya Kamsky]

Technically, when you are using $out you are writing to a new collection and an _id will generated by MongoDB if one is not already provided.

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