[
https://issues.apache.org/jira/browse/SOLR-2155?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12925001#action_12925001
]
David Smiley commented on SOLR-2155:
------------------------------------
bq. Using the canonical geohash gives facet values that can be copy&pasted with
other software. Thinking again, this is a great feature. Would it be worth
optimizing geohash with a Trie version? Trie fields (can be made to) show up
correctly in facets.
The geohash usage is purely internal to the implementation; users don't see it
when they use this field. And even if they were exposed, they can be generated
on-demand. There's even javascript code I've seen to do this. So I'm not
married to using geohashes -- it's the underlying heirarchical/gridded nature
of them that is key. 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.
Thanks for the suggestion of using OpenStreetMaps to get locations; I'll look
into that. I want to put together a useful data set -- using real data as much
as possible is good. I'll need to synthesize a one-to-many document to points
mapping, randomly, however. And I'll need to come up with various random
lat-lon box queries to perform. I'd like to use Lucene's benchmark contrib
module as a framework to develop the performance test. I read about it in LIA2
and it seems to fit the bill.
> 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: [email protected]
For additional commands, e-mail: [email protected]
