Author: rowan.collins
Description:
BUG MIGRATED FROM SOURCEFORGE
http://sourceforge.net/tracker/?func=detail&aid=949323&group_id=34373&atid=411192
Originally submitted by IMSoP 2004-05-06 17:37
There have been numerous instances that I know of on
the English Wikipedia of the entire contents of a page
becoming duplicated - i.e. an additional copy of all
text being appended to itself. This is especially
problematic if it happens on large and busy utility or
discussion pages, since it is often not spotted
immediately and therefore leads to each discussion on
the page being forked without anyone realising, and
having to be carefully merged later.
This appears to be caused by users attempting to submit
more than one edit in competition with themselves, and
specifically submitting the same change twice. Since
large pages are likely to load rather slowly after
editing, people *will* think their changes haven't gone
through, and so click the submit button again - forum
software often includes specific filters to overcome
such multiple submissions. It possibly also interacts
with section editing, since this presumably entails
"construction" of the new page content from the form
data and the existing version.
When this was mentioned on the mailing list, Brion
stated: "There is explicitly no edit conflict
resolution between submissions by the same user."
Clearly, the edit created in such circumstances is
inappropriate, somehow concatenating two (probably
identical) versions, rather than over-writing one with
the other. The software needs to do at least one of:
- Treat multiple submissions from the same user as a
normal edit conflict (creating potential confusion if
they just hit the same button twice)
- detect multiple submissions which contain identical
data, and silently accept one or the other
- detect submissions in very quick succession, and
flatten them into one edit (if they are by the same user)
- at the very least, ignore such situations, as now,
but in a sane way - i.e. use the content from one and
only one edit submission, even if the edit was to a
particular section
Related mailing list posts:
http://mail.wikipedia.org/pipermail/wikitech-l/2004-April/009752.html
http://mail.wikipedia.org/pipermail/wikitech-l/2004-April/009750.html
IMSoP
[http://en.wikipedia.org/wiki/User:IMSoP]
- Additional comments (in reverse order) ----
Date: 2004-06-28 22:06
Sender: robert_dodier
Logged In: YES
user_id=501686
Hello, another bit that might help track down this bug --
[[vfd]] got duplicated sometime today (June 28 2004). Maybe
by checking the editing history, it could be determined
which edit yielded the duplication. Hope this helps.
Date: 2004-06-22 00:18
Sender: wfmcwalter
Logged In: YES
user_id=1036616
It seems only to be with section editing. It's not confined
to edits of new sections (although it may be _caused_ by the
unrelated addition of another section). The duplicated
section certainly isn't always the new one.
It seems to happen more often when the system is slow,
leading me to believe it relates to a user resubmitting an
edit believing it to be "stuck". But that alone isn't
sufficient to cause it.
It happens occasionally (but frequently enough to be a
problem) on heavily edited pages. Before it returned to a
transclusion-based scheme, [[en:Wikipedia:Votes for
deletion]] would exhibit this behaviour several times per day.
It's going to be nearly impossible to obtain a reasonable
idea what users did to precipitate matters, I'm afraid, because:
- it seems to require interaction of two (or more)
simultaneous editors
- at the time it happens, neither is aware (both writes
seem to succeed without an error)
- by the time the error is discovered (often hours later)
it's unlikely either submitter will be able to recall
sufficient detail
- clearly the window in which this occurs is tiny, making
the chances of a manual attempt at reproducing it
diminishingly small
I figure the only way to be able to reliably reproduce it
will be to set two (or more) bots on the same page, making
section edits.
Date: 2004-06-21 23:53
Sender: vibber
Logged In: YES
user_id=446709
Is this only in section editing?
Is this only when adding new sections? [This has long been known
to
duplicate the added section on double submission, since it simply
adds a
new section to the end of whatever is there.]
Is this when editing existing sections? [This is virtually guaranteed
trouble as sections are numbered in a fashion that is liable
to change.]
Is this when editing whole pages?
Can you reliably reproduce the problem?
When you see it happen, please record *everything* you can. When
the
edit occured, whether it was by section or whole page, whether
any edit
conflicts were involved, how many times submitted, etc.
Date: 2004-06-16 17:06
Sender: imsop
Logged In: YES
user_id=1053535
The introduction of edit conflict merging in 1.3 seems to
have made this problem worse:
Firstly, pages like [[en:VfD]] have gone back to being one
large page, and in general slowness has been rearing its
ugly head a lot. Since if something's going that slowly,
people will be more likely to click save twice, this is
triggering more instances of the bug.
Secondly, some people are reporting problems with section
editing, where sections seem to overwrite each other - see
http://meta.wikipedia.org/wiki/MediaWiki_1.3_comments_and_bug_rep
orts#edit_conflict_management_problem
- which may or may not be due to the new code. Since, from
Brion's comment, the behaviour in these conditions appears
to be essentially "undefined", it seems to me that the new
code could be interfering somehow and making the results
even more confusing.
Either way, this seems to be causing major problems, and
needs to be fixed ASAP.
IMSoP
[http://en.wikipedia.org/wiki/User:IMSoP]
Date: 2004-05-06 18:28
Sender: wfmcwalter
Logged In: YES
user_id=1036616
Here's one instance on en.wikipedia.org's [[Reference desk]]
earlier today:
Change log:
Of these two transactions, the latter seemed to cause the
duplication:
m 15:20, 6 May 2004 .. Bodnotbod (=Wikipedia Talk and
Google= how is suppression of Google indexing of VfD done?)
m 15:26, 6 May 2004 .. Bodnotbod (=Wikipedia Talk and
Google= how is suppression of Google indexing of VfD done?)
URL for the problematic change:
http://en.wikipedia.org/w/wiki.phtml?title=Wikipedia:Reference_de
sk&diff=3472769&oldid=3472734
Version: unspecified
Severity: major