"Duplicate of...[deleted post]"

Question

Some questions are getting closed as duplicates - good, the system is working. Unfortunately, some are getting closed as duplicates of other questions which are already deleted. This leaves all 1-9,999 reputation users left scratching their heads when they try to view the duplicate. Even worse, imagine being the author of the question and having your question closed as a duplicate when the original question isn't accessible.

I think something is wrong. Today I undeleted a question (left it closed) since it was referenced in the close-reason for another question. Comments indicated that people were clearly irritated that they could not access the duplicate

^{[Comment] Ok, who thought it was a good idea to close this as duplicate of a deleted question, which most people cannot even see? For the record, I'm reopening - clearly there's enough interest in this question. – Kobi 14 hours ago
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[Comment] The PosibleDuplicate link is broken. Voting to reopen. – Rahul G 7 hours ago
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[Flag] Closed as duplicate of a deleted question, fail. Thanks for moderating. – {username removed} 14 hours ago}

My undelete-action was short-lived, as a few users returned to delete the post again.

It certainly cannot be desirable to reference posts that the vast majority of users cannot even see, especially when the author of the redundant question cannot see (at the time of writing this, the author has a reputation of 18).

I'm not sure what the solution is to this, but I'd like to hear some ideas.

Questions

Question: Why can’t there be an “ultimate” programming language?
Duplicate of: Why can’t we have a single programming Language?

Answer 1

If the question is a duplicate of a deleted question, then it should be deleted as well!

I suppose I should explain my rationale for this...

There are certain questions which don't really belong on SO that get asked repeatedly: "Why isn't [some obscure language that I just got infatuated with] more popular?", "When will [some product I'm anticipating] be released?", "What's your favorite [something]?", etc. Like all duplicates, they should be closed once identified as such. And like all off-topic questions, they should be removed once closed.

Now, you could merge them with the original and thereby keep all the deleted answers together... but why bother when they're deleted!

That said... In this case, the second question ended up being more popular than the original, and was forced into CW (as is traditional for this sort of popular off-topic discussion question). So it'll probably stick around... Because, we hate fun.

Answer 2

This isn't always easy to prevent -- consider this timeline:

1. question A is posted.
2. question B is posted.
3. question B is closed as a dupe of A.
4. question A is deleted for some reason that isn't relevant to explore.
5. now question B points to an invisible question.

The only way to fix this is by some batch process in the back end that will search for "dangling references" and resolve the graph of dependencies. A dupe should always point to an open and undeleted question; if there is a circular dependency or there is no open/undeleted question to point to, a moderator should step in and merge or undelete (or delete!) questions as needed.

Answer 3

I'm with Shog9 on this: if the original was properly deleted then the duplicated should be as well.

But I have developed a subjective impression that the ease of collecting the requisite close votes depends the category of close that is suggested. My impression of the order is roughly (from easiest to hardest):

1. duplicate (easy as cake (well, waffles))
2. belongs-on-* (usually easy)
3. off topic|too localized|not real
4. subjective and argumentative (sometimes very hard, indeed)

So I suspect what you're seeing is people trying to short cut one of the harder to get closes.

My recommendation: Close with the proper reason, but write a comment along the lines of "We deleted the same topic here: <link> for <reason>."

Answer 4

Couldn't this be solved in a way if there where question backtracks from OQ to dupes?

I mean, a question is marked as duplicate, and the original question will now have a small link list above of bellow the Related Questions pointing to the dupes.

This way, when deleting this question a small pop-up could appear pointing to the dupes, which would already have a relation and be denormalized into the question, without further stressing the server by fetching the possible dupes at closing time.

Answer 5

Following on from @Ether's use case, in my opinion when

1. question A is posted.
2. question B is posted.
3. question B is closed as a dupe of A.
4. question A is deleted for some reason that isn't relevant to explore.
5. now question B points to an invisible question.

then

• question B should no longer be marked as a duplicate

This is what seems to have happened already with the question the OP refers to.

Or, at the very least, the text could read something like

Possible Duplicates:

question (deleted)

rather than just

Possible Duplicates:

question

I came across this issue recently as I am trying to learn F#, and searched on google for "best online f# resources". Hurrah I thought as I saw that the 4th result was on stackoverflow: F# learning resources or tutorials. However the duplicated post has been deleted (and in fact only 1 out of the 4 links in the question and its comments works).

This experience wasn't upto the usual good experience I have on stackoverflow, and the moderators aren't able to address it. Removing the duplicate flag on questions that are no longer duplicated seems like an idea worth considering as at least it would stop the frustration of readers being officially directed to click through to a "Page not found". (Ideally if the duplicated post were undeleted, then the duplicate flag would be restored.)