[jira] [Commented] (LUCENE-4978) Spatial search with point query won't find identical indexed point

["David Smiley (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/LUCENE-4978?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13649007#comment-13649007 ] 

David Smiley commented on LUCENE-4978:
--------------------------------------

The offending code is the implementation of IntersectsPrefixTreeFilter's VisitorTemplate.visitScanned:
{code:java}
        if (cell.getLevel() == grid.getMaxLevels() && !cell.isLeaf())
          cShape = cell.getCenter();
        else
          cShape = cell.getShape();
        if (queryShape.relate(cShape).intersects())
          collectDocs(results);
{code}

What's going on here is a performance optimization to use a point for the intersection instead of a rectangle.  I never measured the before-after effect, and I'm not sure if I even thought of it in terms of a performance optimization in the first place although that's what it is.

One possible solution is to see if the query shape is a rectangle or circle; if so then buffer the query shape by 1/2 a grid cell, which is enough to eliminate the possibility of a false-negative. If it's another shape (whether it be a point or a polygon) then use the cell's rect instead of its center point.
                
> Spatial search with point query won't find identical indexed point
> ------------------------------------------------------------------
>
>                 Key: LUCENE-4978
>                 URL: https://issues.apache.org/jira/browse/LUCENE-4978
>             Project: Lucene - Core
>          Issue Type: Bug
>          Components: modules/spatial
>    Affects Versions: 4.1
>            Reporter: David Smiley
>            Assignee: David Smiley
>            Priority: Minor
>
> Given a document with indexed POINT (10 20), when a search for INTERSECTS( POINT (10 20)) is issued, no results are returned.
> The work-around is to not search with a point shape, use a very small-radius circle or rectangle.  (I'm marking this issue as "minor" because it's easy to do this).
> An unstated objective of the PrefixTree/grid approximation is that no matter what precision you use, an intersects query will find all true-positives.  Due to approximations, it may also find some close false-positives.  But in the case above, that unstated promise is violated.  But it can also happen for query shapes other than points which do in fact barely enclose the point given at index time yet the indexed point is in-effect shifted to the center point of a cell which could be outside the query shape, and ultimately leading to a false-negative.

--
This message is automatically generated by JIRA.
If you think it was sent incorrectly, please contact your JIRA administrators
For more information on JIRA, see: http://www.atlassian.com/software/jira

---------------------------------------------------------------------
To unsubscribe, e-mail: dev-unsubscribe@lucene.apache.org
For additional commands, e-mail: dev-help@lucene.apache.org