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High proportion of edit conflicts seem to not involve a conflicting edit
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Description

For context, see the description of T246439. We've instrumented edit conflict and in this case, found a large number of conflicts where the page seems to have not been edited during the edit session, so should not have resulted in a conflict. When EditPage reports baseRevisionId equal to latestRevisionId, the article has not advanced while editing.

select
    sum(if(
        event.baseRevisionId == event.latestRevisionId
            and event.baseRevisionId != 0,
        1, 0)) as unedited,
    count(*) as total
from twocolconflictconflict
where
    year=2020 and month=1;

unedited   total
1927       5263

This happens at the same rate with the legacy and new TwoColConflict interfaces, it's coming from EditPage logic.

From reading the code, these are my initial guesses as to the cause:

  • The deprecated edittime parameter can cause a conflict if it was incorrectly set or changed in the edit form.
  • Section replace failure
  • doEditContent return values can trigger a conflict.

Event Timeline

awight created this task.Feb 28 2020, 1:36 PM
Restricted Application added a subscriber: Aklapper. · View Herald TranscriptFeb 28 2020, 1:36 PM

Change 576901 had a related patch set uploaded (by Awight; owner: Awight):
[mediawiki/extensions/TwoColConflict@master] Log debugging information at start of conflicts

https://gerrit.wikimedia.org/r/576901

Change 576901 merged by jenkins-bot:
[mediawiki/extensions/TwoColConflict@master] Log debugging information at start of conflicts

https://gerrit.wikimedia.org/r/576901

WDoranWMF removed Pchelolo as the assignee of this task.Mar 24 2020, 8:45 PM
WDoranWMF triaged this task as Medium priority.
WDoranWMF raised the priority of this task from Medium to Needs Triage.
WDoranWMF triaged this task as Medium priority.
WDoranWMF added a subscriber: Pchelolo.

Change 596653 had a related patch set uploaded (by Awight; owner: Awight):
[analytics/wmde/TW/edit-conflicts@master] Start investigating same-revision conflicts

https://gerrit.wikimedia.org/r/596653

CCicalese_WMF added a subscriber: CCicalese_WMF.

Is there anything for Core Platform Team to do on this task at this point?