No way to $project out just the _id field in aggregation

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    • Type: New Feature
    • Resolution: Done
    • Priority: Major - P3
    • 3.3.11
    • Affects Version/s: None
    • Component/s: Aggregation Framework
    • None
    • Fully Compatible
    • Query 18 (08/05/16)
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    • 3
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      The command 

      db.example.aggregate([{$project: {_id: 0}}])

      fails because "$project requires at least one output field." Now that $project supports exclusion of other fields, it would be nice if it supports exclusion of just the _id field.

      Interestingly, I can enforce "exclusion mode" by projecting out a field that doesn't exist:

      > db.example.find()
{ "_id" : ObjectId("576d9dc03fcfa43a8b713c74"), "a" : { "a1" : 5, "a2" : 6 }}
{ "_id" : ObjectId("57716feaf6545b026b3dfca1"), "a" : { "a1" : 3, "a2" : 7 }}
> db.example.aggregate([{$project: {_id: 0, c: 0} }])
{"a" : {"a1":5, "a2":6 } , "b":4 }
{"a" : {"a1":3, "a2":7 }}

              Assignee:
              Sally McNichols (Inactive)
              Reporter:
              Carly Robison (Inactive)
              Votes:
              1 Vote for this issue
              Watchers:
              9 Start watching this issue

                Created:
                Updated:
                Resolved: