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From "Michael McCandless (JIRA)" <j...@apache.org>
Subject [jira] Created: (LUCENE-1177) IW.optimize() can do too many merges at the very end
Date Tue, 12 Feb 2008 13:31:10 GMT
IW.optimize() can do too many merges at the very end
----------------------------------------------------

                 Key: LUCENE-1177
                 URL: https://issues.apache.org/jira/browse/LUCENE-1177
             Project: Lucene - Java
          Issue Type: Bug
          Components: Index
    Affects Versions: 2.3
            Reporter: Michael McCandless
            Assignee: Michael McCandless
            Priority: Minor
             Fix For: 2.4


This was fixed on trunk in LUCENE-1044 but I'd like to separately
backport it to 2.3.

With ConcurrentMergeScheduler there is a bug, only when CFS is on,
whereby after the final merge of an optimize has finished and while
it's building its CFS, the merge policy may incorrectly ask for
another merge to collapse that segment into a compound file.  The net
effect is optimize can spend many extra iterations unecessarily
merging a single segment to collapse it to compound file.

I believe the case is rare (hard to hit), and maybe only if you have
multiple threads calling optimize at once (the TestThreadedOptimize
test can hit it), but it's a low-risk fix so I plan to commit to 2.3
shortly.



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