[DOCS-15563] Add note on mapReduce changes to 4.4 compatibility page Created: 23/Aug/22  Updated: 30/Oct/23  Resolved: 24/Aug/22

Status: Closed
Project: Documentation
Component/s: manual, Server
Affects Version/s: 4.4.0
Fix Version/s: Server_Docs_20231030

Type: Task Priority: Major - P3
Reporter: Katya Kamenieva Assignee: Jeffrey Allen
Resolution: Done Votes: 0
Labels: None
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Issue Links:
Related
related to SERVER-68766 Add option to re-enable single value ... Closed
Participants:
Days since reply: 1 year, 22 weeks, 1 day ago
Epic Link: DOCSP-12974

 Description   

in 4.4 there was a change in behaviour of MapReduce.
In 4.2:
"MongoDB will not call the reduce function for a key that has only a single value. The values argument is an array whose elements are the value objects that are "mapped" to the key." docs
From 4.4 onwards, the reduce function will be called regardless of how many values are associated with a given key.

Need to highlight is in the 4.4 upgrade docs, as it's braking for some customers



 Comments   
Comment by Githook User [ 06/Sep/22 ]

Author:

{'name': 'Jeff Allen', 'email': 'jeffrey.allen@10gen.com', 'username': 'jeff-allen-mongo'}

Message: (DOCS-15563): Fix inaccurate mapReduce behavior (#1704)

  • fix heading wording
  • fix broken ref
Comment by Githook User [ 23/Aug/22 ]

Author:

{'name': 'Jeff Allen', 'email': 'jeffrey.allen@10gen.com', 'username': 'jeff-allen-mongo'}

Message: (DOCS-15563): Fix inaccurate mapReduce behavior (#1704)

  • fix heading wording
  • fix broken ref
Comment by Githook User [ 23/Aug/22 ]

Author:

{'name': 'Jeff Allen', 'email': 'jeffrey.allen@10gen.com', 'username': 'jeff-allen-mongo'}

Message: (DOCS-15563): Fix inaccurate mapReduce behavior (#1704)

  • fix heading wording
  • fix broken ref
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