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From Paul Mellor <pmel...@hemscott.co.uk>
Subject RE: Concurrent searching & re-indexing
Date Thu, 17 Feb 2005 10:44:32 GMT
"on windows you cannot delete open files, so Lucene AFAIK (I don't use
windows) postpones the deletion to a time, when the file is closed"

If Lucene does not in fact postpone the deletion, that would explain the
exception I'm seeing ("java.io.IOException: couldn't delete _a.f1") - the
IndexWriter is attempting to delete the files but the IndexReader has them
open.

Does this then mean that re-indexing whilst searching is inherently unsafe,
but only on Windows?

-----Original Message-----
From: Morus Walter [mailto:morus.walter@tanto.de]
Sent: 17 February 2005 10:38
To: Lucene Users List
Subject: RE: Concurrent searching & re-indexing


Paul Mellor writes:
> 
> 1. If IndexReader takes a snapshot of the index state when opened and then
> reads the files when searching, what would happen if the files it takes a
> snapshot of are deleted before the search is performed (as would happen
with
> a reindexing in the period between opening an IndexSearcher and using it
to
> search)?
> 
On unix, open files are still there, even if they are deleted (that is,
there is no link (filename) to the file anymore but the file's content
still exists), on windows you cannot delete open files, so Lucene 
AFAIK (I don't use windows) postpones the deletion to a time, when the 
file is closed.
 
> 2. Does a similar potential problem exist when optimising an index, if
this
> combines all the segments into a single file?
> 
AFAIK optimising creates new files.

The only problem that might occur, is opening a reader during index change
but that's handled by a lock.

HTH
	Morus

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