[SERVER-29669] 'parallelCollectionScan' should always return a single cursor for capped collections Created: 15/Jun/17  Updated: 30/Oct/23  Resolved: 25/Jul/17

Status: Closed
Project: Core Server
Component/s: Replication
Affects Version/s: None
Fix Version/s: 3.5.11

Type: Improvement Priority: Major - P3
Reporter: William Schultz (Inactive) Assignee: Jason Chan
Resolution: Fixed Votes: 0
Labels: None
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Attachments: File test_parallelCollectionScan_insertion_order.js    
Backwards Compatibility: Fully Compatible
Participants:

 Description   

The correctness of opening multiple cursors on a capped collection and reading from them in parallel is potentially problematic and internal support for such an operation is not well defined. Since the 'parallelCollectionScan' command is going to be integrated into the initial sync process, for parallel collection cloning, correctness of this command for capped collections is important. Therefore, its behavior should be simplified to always return a single cursor when run against a capped collection, just like a normal 'find' command would.

In the future, parallel scan support for capped collections may be officially added, but until its correctness can be guaranteed, it should be suitable to resort to this simpler approach.



 Comments   
Comment by Githook User [ 25/Jul/17 ]

Author:

{'name': 'Jason Chan', 'email': 'jason.chan@mongodb.com'}

Message: SERVER-29669 parallelCollectionScan should always return a single cursor for capped collections
Branch: master
https://github.com/mongodb/mongo/commit/4e27af1e980a5f5479fc26a3d616a5b56245261a

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