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Posted to dev@lucene.apache.org by "Oleg Shevelyov (JIRA)" <ji...@apache.org> on 2012/05/11 19:00:55 UTC

[jira] [Commented] (SOLR-2155) Geospatial search using geohash prefixes

    [ https://issues.apache.org/jira/browse/SOLR-2155?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13273417#comment-13273417 ] 

Oleg Shevelyov commented on SOLR-2155:
--------------------------------------

Hi David, does new 1.0.5 version include polygon search? If not, please, could you clarify where to apply GeoHashPrefixFilter patch? It doesn't match solr 3.1 sources, and obviously higher versions as well. I saw you mentioned that you successfully implemented polygon search but I still don't get how to make it work. Thanks
                
> 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: David Smiley
>         Attachments: GeoHashPrefixFilter.patch, GeoHashPrefixFilter.patch, GeoHashPrefixFilter.patch, SOLR-2155_GeoHashPrefixFilter_with_sorting_no_poly.patch, SOLR.2155.p3.patch, SOLR.2155.p3tests.patch, Solr2155-1.0.2-project.zip, Solr2155-1.0.3-project.zip, Solr2155-1.0.4-project.zip, Solr2155-for-1.0.2-3.x-port.patch
>
>
> {panel:title=NOTICE} The status of this issue is a plugin for Solr 3.x located here: https://github.com/dsmiley/SOLR-2155.  Look at the introductory readme and download the plugin .jar file.  Lucene 4's new spatial module is largely based on this code.  The Solr 4 glue for it should come very soon but as of this writing it's hosted temporarily at https://github.com/spatial4j.  For more information on using SOLR-2155 with Solr 3, see http://wiki.apache.org/solr/SpatialSearch#SOLR-2155  This JIRA issue is closed because it won't be committed in its current form.
> {panel}
> 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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