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From Bill Bell <billnb...@gmail.com>
Subject Re: [jira] [Commented] (SOLR-2155) Geospatial search using geohash prefixes
Date Sun, 18 Mar 2012 05:52:53 GMT
I updated the Spatial wiki

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720-256-8076

On Mar 13, 2012, at 8:31 AM, "David Smiley (Commented) (JIRA)" <jira@apache.org> wrote:

> 
>    [ https://issues.apache.org/jira/browse/SOLR-2155?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13228408#comment-13228408
] 
> 
> David Smiley commented on SOLR-2155:
> ------------------------------------
> 
> Harley,
>  Apparently I haven't been clear because this question does come up often, and I sympathize
with you all because the comments on this issue are ridiculously long.  What I should have
done and still can do is add info to the Solr wiki.  Ever since ~September 2011, you no longer
need to patch Solr and you can use any 3x release.  The specific comment with further info
announcing this is:
> https://issues.apache.org/jira/browse/SOLR-2155?focusedCommentId=13117350&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-13117350
> If you look at the attachments to the issue, you'll notice the latest version is 1.0.3.
> 
> When Solr 3.6 comes out (soon!), my co-author and I will write an online addendum to
discuss the changes in Solr 3.5 & Solr 3.6 that affect the content of the book, or are
interesting things that we would have written about if we were still writing it.  I'll add
a clarification to the existing info box on 144 mentioning SOLR-2155 that this feature is
available in plugin form to 3x without patching Solr.
> 
> 
> 
>> 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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