[SERVER-82099] WiredTigerRecordStore searchNear fails on backwards searches with oplog read timestamp Created: 11/Oct/23  Updated: 20/Nov/23  Resolved: 20/Nov/23

Status: Closed
Project: Core Server
Component/s: None
Affects Version/s: None
Fix Version/s: 7.3.0-rc0

Type: Bug Priority: Major - P3
Reporter: Matthew Russotto Assignee: Daotang Yang
Resolution: Fixed Votes: 0
Labels: None
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Issue Links:
Related
related to SERVER-82596 Improve StorageInterfaceImpl::findOpl... Blocked
Assigned Teams:
Storage Execution
Backwards Compatibility: Fully Compatible
Sprint: Execution Team 2023-11-13, Execution Team 2023-11-27
Participants:

 Description   

If you have a recovery unit with an oplog read timestamp which is between records (that is, there is no oplog entry with that read timestamp), then a backwards seekNear on a record ID corresponding to the oplog read timestamp or any later record ID will return boost::none instead of the proper previous record.

I believe a similar problem could theoretically occur with visibility on forward searches, but it never does because WT search_near always returns the next record if it exists.



 Comments   
Comment by Githook User [ 20/Nov/23 ]

Author:

{'name': 'Daotang Yang', 'email': 'daotang.yang@mongodb.com', 'username': ''}

Message: SERVER-82099 Fix WiredTigerRecordStore searchNear fails on backwards searches with oplog read timestamp
Branch: master
https://github.com/mongodb/mongo/commit/13a6e319047593e0b1d60ef41fce0ae352abb37e

Comment by Steven Vannelli [ 23/Oct/23 ]

Thanks matthew.russotto@mongodb.com. We'll consider keep it as 7.3 targeted but will let you know if that changes.

Comment by Matthew Russotto [ 18/Oct/23 ]

steven.vannelli@mongodb.com We may want to start using seekNear on the oplog as part of a (not yet out of the tiger team) performance improvement project, but I'm not actually blocked right now.

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