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https://issues.apache.org/jira/browse/SOLR-2155?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12994123#comment-12994123
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David Smiley commented on SOLR-2155:
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There is no committer assigned, as you can see. After sorting (less so
polygon), I suspect it'll do enough to get enough committer interest.
1. Sorting without a geo filter does present a challenge; this is something
I've been thinking about. However, haversine is only evaluated for each
matching result. If there aren't many, then it isn't too bad. If there are
many, then the only thing I can think of would be to try and only get the
distance for points in a geo-hash box filter at the query center, assuming
you're only looking at the top-10 results. If there aren't enough results in
the box to fill the top-10 then you could either recursively expand the
geo-hash box or give-up on being smart and traverse the remaining matched
documents. Figuring out how to guess a suitable initial box size might be
tricky.
2. My latest geohash field indexes at every intermediate resolution. So if you
were looking through the index values looking for the actual full-detail
points, you'd need to filter out those that aren't long enough.
3. You're only getting one value out of the field cache because each
term/geohash (i.e. point) is a separate value. I confess to not having coded
with the field cache and value sources yet. It has first class support for
single-value per document but multi-value was added later and I don't yet know
what's involved.
> 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.p2.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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