David Smiley created LUCENE-4550:
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Summary: 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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