What happened to this question? When I saw it in the review queue, it had 3 votes to migrate to MSE, and 1 vote to close (Yemon's custom reason). But after I cast the last vote to close, it is now put on hold instead of being migrated. Is there an obvious reason why the migration failed?

(For the record, I voted to close because there is already a duplicate on MSE and it felt like it made sense to merge the two versions together at the site where it appears more suitable, given the current phrasing.)

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    $\begingroup$ The question has now been migrated to math.stackexchange.com. $\endgroup$ Commented Mar 5, 2014 at 16:57
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    $\begingroup$ I think you gave the reason yourself. The question would be a dupe on target site and this is reason for automatic rejection (I am pretty sure I read that recently on meta.SO but cannot find it ATM if I find a source I will upgrade tp an answer). $\endgroup$
    – user9072
    Commented Mar 5, 2014 at 19:02
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    $\begingroup$ @quid No, only the other closure reasons make the migration be rejected. Closing as a duplicate is an exception (unless they changed this). $\endgroup$ Commented Mar 6, 2014 at 8:38
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    $\begingroup$ @TobiasKildetoft we are talking about different types of mig rej. You're right for usual (user caused) rejections. But I talk about automatic rej, ie, one done without any user action on target site, even somehow before the question arrived on target site. Checking the questions edit hist you can see this was instant, the q never arrived on math.SE to be closed there. This auto rej happens AFAIK (at least) for no matching tag, OP (question) banned on target, and duplicate detected by software. I might misremember but I mentioned this slightly before in chat in a different context. $\endgroup$
    – user9072
    Commented Mar 6, 2014 at 10:42
  • $\begingroup$ @quid Ahh, thanks for the clarification. $\endgroup$ Commented Mar 6, 2014 at 11:22
  • $\begingroup$ @FrançoisG.Dorais: thanks. Did the question show up in the failed migration logs that mods have access to? If so, does it give a reason? $\endgroup$ Commented Mar 6, 2014 at 15:55
  • $\begingroup$ @quid: where did you see that? The MSO faq on migration only mentions Q-bans and tag problems. $\endgroup$ Commented Mar 6, 2014 at 15:57
  • $\begingroup$ I don't recall where I saw it, else I could find the source. And, I also checked the FAQ you linked and noted it is not there. Still I am pretty sure I saw it. While I could imagine my memory playing tricks on me here as you set the context it is more difficult for me to imagine I dreamt up what I wrote in chat before chat.stackexchange.com/transcript/message/14058678#14058678 As I say I might misrember of have misunderstood it. Sorry that I cannot say more than: I am pretty sure I read it but I cannot find it now. $\endgroup$
    – user9072
    Commented Mar 6, 2014 at 16:03
  • $\begingroup$ I'm looking into this because it doesn't appear to be due to tags, or the user's ability to ask questions. What remains is that another identical version of the question was on Math prior to this being migrated, but I'm not aware of any duplicate content checks. $\endgroup$
    – Tim Post
    Commented Mar 17, 2014 at 6:37
  • $\begingroup$ OT to answer a question on a now deleted question: I do not know exactly when/why migrations meta->main became imposisble but it seems like a global recent change. The issue is that not rarely questions asked by mistake on meta are such that they might be closed on main too (at least initially). Then, one has a rejected migration and the ensuing mess (question being locked on main where it should be improved...). The idea was for example mentioned on meta.math by a user known by many names, on a feature-request by Asaf. Possibly, they pushed through the change, which I find an improvement. $\endgroup$
    – user9072
    Commented Apr 28, 2015 at 13:09

1 Answer 1


I updated the meta post. Another byte by byte copy of that question existed on Math SE prior to the migration, which is why it was automatically rejected by the system.

We do appear to log this, I'm going to investigate getting the reason for the automatic rejection to be visible in the question's timeline that is visible to moderators.

I'm not certain when we started duplicate content checking on migration events, but I don't think it was recent - just rare enough that it's not easily noticed.

  • $\begingroup$ It would be continuously creepy if there isn't a first time that this happened, but it never happened before 2014. Also quantum creepy. $\endgroup$
    – Asaf Karagila Mod
    Commented Mar 17, 2014 at 10:27
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    $\begingroup$ Some people on MathOverflow and Math.StackExchange want to prevent multiple identical posts on those two sites, and discourage simultaneous cross-posting. As described by Willie Wong in the question, that was partly the motivation for this failed migration. In fact, I also voted to migrate the question for the same reason. The check for duplicate content which you describe specifically prevented the intended migration. Do you have any comments or suggestions? $\endgroup$ Commented Mar 17, 2014 at 15:38
  • $\begingroup$ I believe there was another case of a failed migration due to there already being a duplicate at the target site: the question mathoverflow.net/questions/162427/accelerating-em-algorithm is a duplicate of stats.stackexchange.com/questions/92281… (even though the titles are different) and appears to have failed to migrate to stats.stackexchange.com upon its closure. $\endgroup$ Commented Apr 4, 2014 at 17:34

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