[SERVER-29151] Does wiredtiger.truncate satisfy the snapshot-isolation sematics? Created: 12/May/17  Updated: 12/May/17  Resolved: 12/May/17

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

Type: Question Priority: Major - P3
Reporter: deyukong Assignee: Unassigned
Resolution: Done Votes: 0
Labels: None
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Participants:

 Description   

In oplog cleaning, mongo use session->truncate to cleanup oldest oplogs.
Which may still be held by snapshot-manager's uncommitted_snapshots.
If session->truncate does not satisfy snapshot-isolation, snapshot-manager's uncommitted_snapshots are not dropped but the data are deleted.
If session->truncate does satisfy snapshot-isolation, link SERVER-29150 should be a problem?



 Comments   
Comment by deyukong [ 12/May/17 ]

OK, thanks. I will forward this question into the group.

Comment by Eric Milkie [ 12/May/17 ]

Thanks for your report. Please note that SERVER project is for reporting bugs or feature suggestions for the MongoDB server. For MongoDB-developer related support discussion please post on the mongodb-dev group. A question like this involving more discussion would be best posted on the mongodb-dev group.

Comment by Eric Milkie [ 12/May/17 ]

WiredTiger's fast truncate() does support read isolation levels appropriately, including snapshot isolation. As described in SERVER-29150, performance will suffer if the committed snapshot does not move but new writes continue to happen.

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