[SERVER-31748] Allow $count/$size in $graphLookup Created: 27/Oct/17  Updated: 06/Dec/22

Status: Backlog
Project: Core Server
Component/s: Aggregation Framework
Affects Version/s: None
Fix Version/s: None

Type: New Feature Priority: Major - P3
Reporter: Jose Assignee: Backlog - Query Optimization
Resolution: Unresolved Votes: 0
Labels: None
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Assigned Teams:
Query Optimization
Participants:

 Description   

There are many times that you don't need to retrieve the documents from a graphLookup, you only want the number of resulting documents after performing the graphLookup stage, you are throwing away capacity in the process, if you after the graphLookup are going to do a $size operation.

If the graphLookup could resolve in a number being this number the count of the resulting documents, could be way more easy to retrieve the needed data without having to use so many resources.



 Comments   
Comment by James Wahlin [ 27/Oct/17 ]

Hi Jose,

The feature you request will be available for $lookup in MongoDB 3.6 and can be tested in our 3.6.1-rc1 release candidate. We are introducing a new $lookup syntax that lets you specify your own foreign pipeline syntax. You can learn more about on the following page:

https://docs.mongodb.com/master/reference/operator/aggregation/lookup/#join-conditions-and-uncorrelated-sub-queries

Given this I am going to narrow the scope of this feature request to $graphLookup, which does not yet have this capability and won't for 3.6.

Thanks,
James

Comment by Mark Agarunov [ 27/Oct/17 ]

Hello jgl,

Thank you for the detailed description. I've set the fixVersion to "Needs Triage" for this new feature to be scheduled against our currently planned work. Updates will be posted on this ticket as they happen.

Thanks,
Mark

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