From mongodb docs
You can $project the results to exclude the _id
- is this what you mean?
http://docs.mongodb.org/manual/reference/aggregation/#pipeline
Note The _id field is always included by default. You may explicitly exclude _id as follows:
db.article.aggregate(
{ $project : {
_id : 0 ,
title : 1 ,
author : 1
}}
);
From you're example, the first operation in the pipeline would be to exclude the _id and include the other attribs.