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From Scott Smith <>
Subject RE: Lucene reorganizing indexes
Date Tue, 17 Jul 2012 21:07:01 GMT
It's lucene

-----Original Message-----
From: Ralf Heyde [] 
Sent: Monday, July 16, 2012 10:42 PM
Subject: AW: Lucene reorganizing indexes 

Do you use Lucene or Solr?

We faced the problem in Solr due too big Caches, which where (re)warmed up after a commit
and the never ending full GCs.

Greets Ralf

-----Urspr√ľngliche Nachricht-----
Von: Scott Smith []
Gesendet: Montag, 16. Juli 2012 22:29
Betreff: Lucene reorganizing indexes 

We have an application that has to do "real time" indexing of a number of documents.  What
it does is wake up about every 20 seconds and updates the index with any changes that have
been queued since the last time it ran.
This involves adding and deleting several hundred documents.  This is all done in a single
thread.  There can be multiple threads doing searches simultaneous with the update thread
(the searches run in a different process).

Back in the days of 1.42, we would force an index optimization once each day.  However, my
impression is that the later versions of Lucene (we are currently using 3.5), Lucene will
often do its own reorganization based on hitting certain criteria.  I've been told that optimizing
the index is, perhaps, no longer necessary.  Can someone describe what happens here?

The reason I'm asking about this is that we see our application periodically using excessive
amounts of kernel time (on Windows) which normally indicates a lot of disk activity.  We are
unable to align this with anything our code is doing.  Obviously, we expect Lucene to be causing
disk activity, it just seems that the last release (we were at 3.02 before going to 3.5) severely
increased the disk activity which is interfering with other things running on the boxes.

Does any of this make sense to anyone?  Is there an explanation?  Thoughts about what we might
do about it?

Thanks in advance.


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