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From Michael McCandless <>
Subject Re: Reviving a dead index
Date Thu, 23 Nov 2006 11:39:19 GMT
Aleksander M. Stensby wrote:
> Hey, saw this old thread, and was just wondering if any of you solved 
> the problem? Same has happened to me now. Couldn't really trace back to 
> the origin of the problem, but the segments file references a segment 
> that is obviously corrupt/not complete...
> I thought i might remove the uncomplete segment, but then i guess this 
> would f* up my segments file. Any taker on how to remove the segment in 
> question, and make the rest of the index work again?.. Since i guess its 
> not as straightforward to just remove the segmentname from the segments 
> file without changing some of the other crytic bytes aswell..?

I don't think the root cause was ever uncovered on this thread.

Do you have any copying process to move your index from one machine to
another, or across mount points on the same machine, or anything?  A
copying step has been the cause of similar corruption in past issues.
I would really like to get to the root cause of any and all

To recover your index, it would be fairly simple to write a tool that
reads the segments files, removes the known bad segments, and writes
the segments file back out.  Something like this (I haven't tested!):

   Directory dir = FSDirectory.getDirectory("/path/to/my/index", false);
   SegmentInfos sis = new SegmentInfos();;
   for(int i=0;i<sis.size();i++) {
     SegmentInfo si = (SegmentInfo) sis.elementAt(i);
     if ("_XXXX")) {

Please make a backup copy of your index before running this in case
it messes anything up!!

And note that by removing an entire segment, many documents are now
gone from your index.  Determining which ones are gone and must be
reindexed is not particularly easy unless you have a way to do so in
your application...

Also note that Lucene will not delete the now un-referenced (bad)
segment file (ie, _XXXX.cfs, and other _XXXX files like _XXXX.del if
it exists) so you will have to do that step manually.  (The current
"trunk" version of Lucene does in fact remove unreferenced index
files correctly but this hasn't been released yet).


> - Aleksander
> On Thu, 31 Aug 2006 03:42:28 +0200, Michael McCandless 
> <> wrote:
>> Stanislav Jordanov wrote:
>>> For a moment I wondered what exactly do you mean by "compound file"?
>>> Then I read and 
>>> got the idea.
>>> I do not have access to that specific machine that all this is 
>>> happening at.
>>> It is a 80x86 machine running Win 2003 server;
>>> Sorry, but they neglected my question about the index is stored on a 
>>> Local FS or on a NFS.
>>> I was only able to obtain a directory listing of the index dir and 
>>> guess what - there's no a /*_1j8s.cfs * /file at all!
>>> Pitty, I can't have a look at segments file, but I guess it lists the 
>>> _1j8s
>>> Given these scarce resources, can you give me some further advise 
>>> about what has happened and what can be done to prevent it from 
>>> happening again?
>> I'm assuming this is easily repeated (question from my last email) and
>> not a transient error?  If it's transient, this could be explained by
>> locking not working properly.
>> If it's not transient (ie, happens every time you open this index),
>> it sounds like indeed the segments file is referencing a segment that
>> does not exist.
>> But, how the index got into this state is a mystery.  I don't know of
>> any existing Lucene bugs that can do this.  Furthermore, crashing
>> an indexing process should not lead to this (it can lead to other things
>> like only have a file and no segments file).
>> Were there any earlier exceptions (before indexing hit an "improper
>> shutdown") in your indexing process that could give a clue as to root
>> cause?  Or for example was the machine rebooted and did windows to run
>> a "filesystem check" on rebooting this box (which can remove corrupt
>> files)?
>> Mike
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> --Aleksander M. Stensby
> Software Developer
> Integrasco A/S
> Tlf.: +47 41 22 82 72
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