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Type: Task
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Resolution: Fixed
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Priority: Major - P3
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Affects Version/s: None
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Labels:None
Description
Downstream Change Summary
This ticket adds $count as an accumulator to the $group stage:
{ $count: {} }
is desugared to:
{ $sum: 1 }
Description of Linked Ticket
This task is for adding support for $count as an accumulator to the $group stage.
Scope of changes
New accumulator: https://docs.mongodb.com/manual/reference/operator/aggregation/#accumulators-group
Make sure we update https://docs.mongodb.com/manual/reference/operator/aggregation/group/#count-the-number-of-documents-in-a-collection as part of this change.
Also:
https://docs.mongodb.com/manual/reference/operator/aggregation/count/
Behavior section, current:
db.collection.aggregate( [
{ $group: { _id: null, myCount: { $sum: 1 } } },
{ $project: { _id: 0 } }
] )
Desired:
db.collection.aggregate( [
{ $group: { _id: null, myCount: { $count: {} } } },
{ $project: { _id: 0 } }
] )
Impact to Other Docs
MVP (Work and Date)
Resources (Scope or Design Docs, Invision, etc.)
- documents
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SERVER-54236 Implement $count accumulator
- Closed