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From Ramprakash Ramamoorthy <>
Subject IndexUpgrade - Any ways to speed up?
Date Fri, 02 Aug 2013 11:49:23 GMT

        We are migrating from lucene version 2.3.1 to 4.1. We are migrating
the indices as well, and we do this in two steps 2.3.1 to 3.6.2 and 3.6.2
to 4. We just call IndexUpgrader.upgrade(), using the
IndexUpgraderMergePolicy. I see that, the upgrade() method actually calls a
forcemerge(1) over the indices.

        However, we have all our indices optimized and there are no deletes
as well. This forcemerge(1) seems a very costly operation and since our
index is already optimized, there is no space benefit as well. Is there a
faster way to upgrade our indices (like reading the indices and modifying
the headers, something of that sort)? We are not expecting any compaction
during the process.

         Currently it takes 4 minutes for a GB of index to get migrated to
4.1 from 2.3.1. Any pointers would be appreciated. Thanks in advance.

With Thanks and Regards,
Ramprakash Ramamoorthy,
Chennai, India.

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