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From "Harley Parks (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (SOLR-2155) Geospatial search using geohash prefixes
Date Sun, 18 Mar 2012 03:27:58 GMT

    [ https://issues.apache.org/jira/browse/SOLR-2155?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13232139#comment-13232139
] 

Harley Parks commented on SOLR-2155:
------------------------------------

Bill: 

the main advantage is gh_geofilt (or the name in queryParser settup in solrconfig.xml) can
be used as part of the query versus the filter... at least that is what I thought... here
are my test strings in solr/admin/form

it might be helpful to be able to pass parameters in like geodist(sfield,lat,lng).
gh_geofilt(sfield,lat,lng,d) 

this worked for me in the solr/admin/form:

!gh_geofilt sfield=GeoTagGeoHash pt=-9,160 d=5


this also worked for me in the solr/admin/form:

!gh_geofilt sfield=GeoTagGeoHash point=-9,160 radius=5

but this also worked:
!geofilt sfield=GeoTagGeoHash point=-9,160 radius=5
!geofilt sfield=GeoTagGeoHash pt=-9,160 d=5


                
> 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
>         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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