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https://issues.apache.org/jira/browse/LUCENE-4550?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13560045#comment-13560045
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Commit Tag Bot commented on LUCENE-4550:
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[trunk commit] David Wayne Smiley
http://svn.apache.org/viewvc?view=revision&revision=1437182
LUCENE-4550: fix SpatialArgs.calcDistanceFromErrPct
> 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
> Assignee: David Smiley
> Priority: Minor
> Attachments: LUCENE-4550__fix_SpatialArgs_calcDistanceFromErrPct.patch
>
>
> 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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