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From "Robert Tseng (JIRA)" <>
Subject [jira] [Commented] (SOLR-2155) Geospatial search using geohash prefixes
Date Wed, 17 Oct 2012 06:20:07 GMT


Robert Tseng commented on SOLR-2155:

Hi All,

New to Solr here!  I have a question for you all on gh_geofilt.  My document has rows of path,
think of KML lineString, of which I want to do bounding box check which of them fall within
a box.  Each row basically has an id field and a multivalued field describing the line with
multiple points.

What I want returned is all lines that fall within but I read Solr is not very good, yet,
in returning large number of hits.  Hence the row params to limit result to top N rows.  My
two questions are:

1. If want to retrieve all rows, do I query twice from solrj.  Once to get number of hits
so I can set the number of rows that grabs all row in a second call? Or two I should chunk
up the query call using the start params as an offset? 

2. If it's only returning top N, is it based on score?  What is considered high score? A row
with most number of hits in the box? Cloest to the center?
> Geospatial search using geohash prefixes
> ----------------------------------------
>                 Key: SOLR-2155
>                 URL:
>             Project: Solr
>          Issue Type: Improvement
>            Reporter: David Smiley
>            Assignee: David Smiley
>         Attachments: GeoHashPrefixFilter.patch, GeoHashPrefixFilter.patch, GeoHashPrefixFilter.patch,,,, Solr2155-for-1.0.2-3.x-port.patch,
SOLR-2155_GeoHashPrefixFilter_with_sorting_no_poly.patch, SOLR.2155.p3.patch, SOLR.2155.p3tests.patch
> {panel:title=NOTICE} The status of this issue is a plugin for Solr 3.x located here:  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
 For more information on using SOLR-2155 with Solr 3, see
 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 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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