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https://issues.apache.org/jira/browse/SOLR-2155?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13070339#comment-13070339
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David Smiley commented on SOLR-2155:
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Bill, have you checked out LSP?: 
http://code.google.com/p/lucene-spatial-playground/  A couple folks have been 
kicking the tires last week.  We've got some benchmarking and (more) testing to 
do, and there's still the polygon date-line & pole wrapping feature-gap that 
hasn't been implemented yet. There's always more I want to do with it but its 
in decent shape now. It can even index shapes with area (i.e. not just points 
but other shapes) -- the only Lucene/Solr native implementation that I know of, 
Ryan too.

> Geospatial search using geohash prefixes
> ----------------------------------------
>
>                 Key: SOLR-2155
>                 URL: https://issues.apache.org/jira/browse/SOLR-2155
>             Project: Solr
>          Issue Type: Improvement
>            Reporter: David Smiley
>            Assignee: Grant Ingersoll
>         Attachments: GeoHashPrefixFilter.patch, GeoHashPrefixFilter.patch, 
> GeoHashPrefixFilter.patch, 
> SOLR-2155_GeoHashPrefixFilter_with_sorting_no_poly.patch, SOLR.2155.p3.patch, 
> SOLR.2155.p3tests.patch
>
>
> There currently isn't a solution in Solr for doing geospatial filtering on 
> documents that have a variable number of points.  This scenario occurs when 
> there is location extraction (i.e. via a "gazateer") occurring on free text.  
> None, one, or many geospatial locations might be extracted from any given 
> document and users want to limit their search results to those occurring in a 
> user-specified area.
> I've implemented this by furthering the GeoHash based work in Lucene/Solr 
> with a geohash prefix based filter.  A geohash refers to a lat-lon box on the 
> earth.  Each successive character added further subdivides the box into a 4x8 
> (or 8x4 depending on the even/odd length of the geohash) grid.  The first 
> step in this scheme is figuring out which geohash grid squares cover the 
> user's search query.  I've added various extra methods to GeoHashUtils (and 
> added tests) to assist in this purpose.  The next step is an actual Lucene 
> Filter, GeoHashPrefixFilter, that uses these geohash prefixes in 
> TermsEnum.seek() to skip to relevant grid squares in the index.  Once a 
> matching geohash grid is found, the points therein are compared against the 
> user's query to see if it matches.  I created an abstraction GeoShape 
> extended by subclasses named PointDistance... and CartesianBox.... to support 
> different queried shapes so that the filter need not care about these details.
> This work was presented at LuceneRevolution in Boston on October 8th.

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