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From "David Smiley (JIRA)" <>
Subject [jira] [Created] (LUCENE-4550) For extremely wide shapes (> 180 degrees) distErrPct is not used correctly
Date Fri, 09 Nov 2012 16:10:12 GMT
David Smiley created LUCENE-4550:

             Summary: For extremely wide shapes (> 180 degrees) distErrPct is not used
                 Key: LUCENE-4550
             Project: Lucene - Core
          Issue Type: Bug
          Components: modules/spatial
    Affects Versions: 4.0
            Reporter: David Smiley
            Priority: Minor

When a shape is given to a PrefixTreeStrategy (index or query time), it needs to know how
many levels down the prefix tree to go for a target precision (distErrPct).  distErrPct is
basically a fraction of the radius of the shape, defaulting to 2.5% (0.0025).

If the shape presented is extremely wide, > 180 degrees, then the internal calculations
in SpatialArgs.calcDistanceFromErrPct(...) will wrongly measure the shape's size as having
width < 180 degrees, yielding *more* accuracy than intended.  Given that this happens for
unrealistic shape sizes and results in more accuracy, I am flagging this as "minor", but a
bug nonetheless.  Indeed, this was discovered as a result of someone using lucene-spatial
incorrectly, not for an actual shape they have.  But in the extreme [erroneous] case they
had, they had 566k terms (!) generated, when it should have been ~1k tops. 

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