Minor - P4 3.1.4 of the server brings the new $project-stage aggregate expression "$filter", allowing for filtering out elements of arrays which are sub-elements of documents.
This works much like $elemMatch in find() - but in an aggregation pipeline.
- depends on
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SERVER-17943 add $filter expression to $project to work with $map and $reduce
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- Closed
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- is duplicated by
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- Closed
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