[jira] [Commented] (SOLR-2155) Geospatial search using geohash prefixes

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[jira] [Commented] (SOLR-2155) Geospatial search using geohash prefixes

Sebastian Nagel (Jira)

    [ https://issues.apache.org/jira/browse/SOLR-2155?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13240190#comment-13240190 ]

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

Ok so I got to the bottom of this. When I originally coded the cache entry thing, my intention was to use the same cache as UnInvertedField (multi-value faceting) -- THE "fieldValueCache" since it seemed related.  But I did that wrong and instead it looked up a custom user cache by that same name.  The difference is that the official one is configured with <fieldValueCache> and the other is <cache name="fieldValueCache"> (documented in the read me).  In hind site, I should have chosen some special name like "solr2155".  Now, if you don't configure the cache then *each* time you try to sort, it has to rebuild the cache.  So basically it's required to add this cache configuration assuming your sorting.
               

> 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, Solr2155-1.0.4-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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