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David Smiley commented on SOLR-2155:
------------------------------------

bq. You mention: "Sorting by (multi-value) indexed shapes is supported only for 
points". Does this mean that representation 1.) above is supported? It wasn't 
entirely clear for me from your response.

Yes, it does.  This patch & LSP support sorting documents by a multi-value 
point field.

Based on the description of your use-case and my interpretation of what you say 
(which I am not 100% sure of), I don't think it's pertinent that the "walks" 
are polygons. What is pertinent is that they are a collection of points (Pois). 
 So if your "walk" corresponds to a Solr document, you could have a "poi" field 
that is an indexed multi-value geospatial point field. Then you could sort 
walks (documents) according to the pois that are closest to a user-specified 
point in the query.  I would add a large bounding-box filter which would 
improve performance.  It's not clear to me there is any need for polygon 
support.

FYI I use the well-known JTS library for polygon support.


> 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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