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From "Olivier Jacquet (Issue Comment Edited) (JIRA)" <j...@apache.org>
Subject [jira] [Issue Comment Edited] (SOLR-2155) Geospatial search using geohash prefixes
Date Mon, 17 Oct 2011 16:32:10 GMT

    [ https://issues.apache.org/jira/browse/SOLR-2155?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13128980#comment-13128980
] 

Olivier Jacquet edited comment on SOLR-2155 at 10/17/11 4:30 PM:
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I just wanted to mention another use case for multivalued point fields since everyone is always
talking about this in a location context.

The PointType can also be used to categorize other other stuff. In my case we're storing qualifications
of persons as a tuple of experience, function and skill (eg. senior, developer, java) which
are internally represented by numerical ids. Now with Solr I would like to be able to do the
query: "return everything that is a java developer" which would be the same as asking for
all points on a certain plane.
                
      was (Author: ojacquet):
    I just wanted to mention another use case for multivalued point fields since everyone
is always talking about this in a location context.

The PointType can also be used to categorize other other stuff. In my case we're storing qualifications
of persons as a tuple of experience, function and skill (eg. senior, developer, java) which
are internally represented by numerical ids. Now with Solr I would like to be able to do the
query: "return everything that is a java developer" which would be the same as asking for
all points on a certain line.
                  
> 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,
Solr2155-1.0.2-project.zip, Solr2155-1.0.3-project.zip, Solr2155-for-1.0.2-3.x-port.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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