Question about applications using different versions of Lucene

I believe the Lucene file format changed in version 2.1, and your nightly
.jar file is probably v2.1. See
http://lucene.apache.org/java/docs/fileformats.html#Segments%20File.

I'm afraid I'm not an expert on the related compatibility issues. It has
been my experience that pre-2.1 Lucene cannot read 2.1 indexes (error: can't
find segments file). You seem to have shown the converse is also
true...although I could have sworn that Lucene 2.1 slurped my pre-2.1 index
without problems.

Hope this helps,
-Graham



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: I have two applications that share some of the same Lucene Indexes. I
: recently upgrade the Lucene-core.jar from v2.0 to a nightly build (Feb.
: 04, 2006 - I was looking for the IndexWriter class that allows you to
: merge indexes w/o optimizing).

Am I correct in understanding that you have two seperate applications: one
reading hte index and one writing the index and you only upgraded lucene
for the application that writes the index?

If so, this is not a supported compatibility situation, if the wiki were
up right now there is a document that explains...

File formats are back-compatible between major versions. Version X.N
should be able to read indexes generated by any version after and
including version X-1.0, but may-or-may-not be able to read indexes
generated by version X-2.N.

...what happens is that the 2.X code in the trunk can correctly read your
2.1 index, but it modifies hte files on disk as you add documents to morph
the index format to the new 2.X format -- your seperate 2.1 application
can not read that format.

(if i'm in correct and you actually updated the lucene jar for both
applications then please clarify)


-Hoss


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DOH!

Thanks,

Van

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Hi,

I suspect what happened is result of a "mis-ordered" upgrade sequence:
The first of the two applications managed to access and upgrade
the index. However the second application then tried to update the
already upgraded index and messed things up.

I think this may even be worse, as one of the changes since 2.0 is
that write locks are now (by default) maintained in the index directory.
So if the two applications attempt to access the index at the same time,
but one uses 2.0 and the other uses "to-be-2.1" version, since locks
are maintained in different places, they might both write to the index
at the same time and corrupt it.

A related discussion is in this thread:
http://issues.apache.org/jira/browse/LUCENE-771#action_12464409

To conclude, the upgrade steps should be:
1) upgrade all readers.
2) upgrade all writers at once (no old writer should access the
index ones this step started).

Regards,
Doron

"Van Nguyen" <vnguyen@ur.com> wrote on 12/02/2007 16:55:59:

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