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From "Michael McCandless" <luc...@mikemccandless.com>
Subject Re: IndexReader locking index
Date Sat, 01 Dec 2007 09:56:04 GMT

"Ruslan Sivak" <rsivak@istandfor.com> wrote:
> I am using MoreLikeThis functionality in my code.  This code is
> running on four separate servers.

How do your separate servers share the index?  What remote filesytem
are you using here?

> When I ran tests, it seemed to be fine, but looks like under heavy
> use, the index file is always locked,

Which version of Lucene are you using?  Read-only use of the index
(using an IndexReader without using any of its "writing" methods like
deleteDocument or setNorm) should not do any locking against the
index, as of Lucene 2.1.

> and when I reindex all the docs, it doubles the size of the index
> (my guess is the old files are not being deleted).

If you have a reader open on the index, then the reader will hold
these files open so they cannot be deleted (until that reader/readers
close).  If you then fully re-index into that same directory, that
would explain the 2X usage.

> Since my index is only about 11mb, I would like to load it into RAM.
> I'm not sure if this is compatible with MoreLikeThis?  How do I load
> the index into memory and then open and IndexReader on it?

This is simple:

  Directory dir = new RAMDirectory(otherDir)

will load all files in otherDir into RAM.  Then you can pass that dir
to IndexReader.open or IndexSearcher.  This will work fine with
MoreLikeThis and all other searching, etc.  But just remember since
this is a RAMDirectory, if you make any changes to it, they won't be
saved to disk unless you explicitly do so.

> Also if I load it into memory, how can I find out when changes have
> been made to the index file on disk so that I can reload it?

You can call IndexReader.isCurrent() if you have a reader open on the
disk-based Directory, or, IndexReader.getCurrenVersion (static method)
if you don't; when that version number changes, your index has
changed.

Mike

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