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From "Michael McCandless (JIRA)" <j...@apache.org>
Subject [jira] [Created] (LUCENE-3254) BitVector.isSparse is sometimes wrong
Date Tue, 28 Jun 2011 13:49:17 GMT
BitVector.isSparse is sometimes wrong
-------------------------------------

                 Key: LUCENE-3254
                 URL: https://issues.apache.org/jira/browse/LUCENE-3254
             Project: Lucene - Java
          Issue Type: Bug
          Components: core/other
            Reporter: Michael McCandless
            Assignee: Michael McCandless
             Fix For: 3.4, 4.0


In working on LUCENE-3246, I found a few problems with
BitVector.isSparse:

  * Its math can overflow int, such that if there are enough deleted
    docs and maxDoc() is largish, isSparse may incorrectly return true

  * It over-estimates the size of the sparse file, since when
    estimating number of bytes for the vInt dgaps it uses bits.length
    instead of bits.length divided by number of set bits (ie, the
    "average" gap between set bits)

This is relatively harmless (just affects performance / size of .del
file on disk, not correctness).


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