[SERVER-38454] Consider support for field renaming in $unwind stage Created: 07/Dec/18  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: Trivial - P5
Reporter: Jeffrey Mariconda Assignee: Backlog - Query Optimization
Resolution: Unresolved Votes: 1
Labels: None
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Assigned Teams:
Query Optimization
Participants:

 Description   

In my experience, array fields in documents are usually labeled as plural (e.g. items: ['item']). This becomes a little confusing to read once they are past the $unwind stage because the value will become singular but the field name remains plural.  This can be alleviated via an $addFields stage directly after the $unwind, but that seems inefficient.

 

A potential solution here could be to add an 'as' option to the $unwind stage like the following:

 

{ $unwind: { path: '$items', as: 'item' } }

 

This would $unwind and rename the unwound field to the specified name in a single stage, and it is consistent with the naming conventions of expressions like $filter.

 


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