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Type:
New Feature
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Resolution: Done
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Priority:
Major - P3
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Affects Version/s: None
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Component/s: Aggregation Framework
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Labels:None
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Fully Compatible
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Query 18 (08/05/16)
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 }}
- is documented by
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DOCS-8911 No way to $project out just the _id field in aggregation
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- Closed
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- Closed
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- related to
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SERVER-18966 Allow exclusion in $project stage of aggregation pipeline
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- Closed
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