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Date: Fri, 9 Nov 2012 16:10:14 +0000 (UTC)
From: "David Smiley (JIRA)" <jira@apache.org>
To: dev@lucene.apache.org
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Subject: [jira] [Updated] (LUCENE-4550) For extremely wide shapes (> 180
 degrees) distErrPct is not used correctly
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     [ https://issues.apache.org/jira/browse/LUCENE-4550?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

David Smiley updated LUCENE-4550:
---------------------------------

    Description: 
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. 

  was:
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. 

    
> For extremely wide shapes (> 180 degrees) distErrPct is not used correctly
> --------------------------------------------------------------------------
>
>                 Key: LUCENE-4550
>                 URL: https://issues.apache.org/jira/browse/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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