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    Type:Improvement 
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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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    Component/s: Aggregation Framework
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    None
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        Fully Compatible
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        Query 2017-10-23, Query 2017-11-13
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The current implementation of $changeStream's post-update lookup functionality should be refactored for simplicity and performance, by introducing a new lookupSingleDocument method in the MongoProcessInterface auxiliary class.
- is duplicated by
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                    SERVER-31684 QueryPlanKilled (operation exceeded time limit) in $changeStream with updateLookup -         
- Closed
 
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- related to
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                    SERVER-31674 Rename misleading functions and structs in cluster_aggregate.cpp -         
- Closed
 
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