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Lance Norskog commented on SOLR-2155: ------------------------------------- bq. I'm not sure how a "trie version" of geohash is developed. I already spoke of further refining the implementation to index the geohashes at each grid level and I think that is very similar to what trie does for numbers. This is why I mention the Trie classes- they seemed like the same tool, and the lessons learned in making facets etc. work are worth knowing. It seems like a Trie for geohash would just be a character-by-character Trie. > 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 > > > 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. -- This message is automatically generated by JIRA. - You can reply to this email to add a comment to the issue online. --------------------------------------------------------------------- To unsubscribe, e-mail: dev-unsubscr...@lucene.apache.org For additional commands, e-mail: dev-h...@lucene.apache.org