[jira] [Created] (LUCENE-9870) Circle2D intersectsLine bug mostly causes no matches along indexed lines and outside polygon edges

["Jørgen Nystad (Jira)" <ji...@apache.org>]

Jørgen Nystad created LUCENE-9870:
-------------------------------------

             Summary: Circle2D intersectsLine bug mostly causes no matches along indexed lines and outside polygon edges
                 Key: LUCENE-9870
                 URL: https://issues.apache.org/jira/browse/LUCENE-9870
             Project: Lucene - Core
          Issue Type: Bug
          Components: modules/spatial
    Affects Versions: 8.8
            Reporter: Jørgen Nystad


Circle2D intersectsLine does a dot product to determine closest point on line but then filters it like this:
 
{code:java}

    final double distance = dotProduct / magnitudeAB;

    if (distance < 0 || distance > dotProduct) {
      return false;
    }

{code}

If magnitudeAB (squared length of line) is less than 1 (degree), this will always return false.

distance is actually the "t-value", meaning the correct behaviour here would be to clamp it between 0 and 1 to ensure point is on actual line.

A straightforward fix that works since edge and end points are checked anyway:

{code:java}

    final double distance = dotProduct / magnitudeAB;

    if (distance < 0 || distance > 1) {
      return false;
    }

{code}

This is tested and verified by building version 8.8.0 and replacing jar-files in an elasticsearch instance of version 7.12.



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