[DOCS-16286] explain.executionStats.nReturned should be docs returned by the winning plan Created: 31/Jul/23  Updated: 06/Feb/24  Resolved: 06/Feb/24

Status: Closed
Project: Documentation
Component/s: manual, Server
Affects Version/s: None
Fix Version/s: None

Type: Task Priority: Minor - P4
Reporter: Adi Agrawal Assignee: Matthew Maville
Resolution: Done Votes: 0
Labels: backlog, query, quick-win, request
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Issue Links:
Depends
Participants:
Days since reply: 27 weeks, 2 days ago
Story Points: 2

 Description   

Currently, explain.executionStats.nReturned reads: Number of documents that match the query condition. It should instead be the number of documents returned by the winning plan. This subtle difference can be seen in the following scenario:

I have the following docs in my collection:[\{a: 1}, \{a: 2}, \{a: 3}] and run the agg pipeline [{$addFields: {"diff": {$subtract: [5, "$a"]}, {$match: {"diff": {$lte: 2}}}]{}}}, we return 1 doc. When running explain on this aggregate, the winning plan in the case of the classic engine is just COLLSCAN (without any filter) and nReturned is 3. 


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