[michaelt]

I'm no Solr expert, but bug SOLR2155 has a patch [1] that does a geospatial search using geohash prefixes [2].

As far as I can tell, you take the point's latitude and longitude and interleave the binary bits - so if your record's latitude is 11111111 and your longitude is 10000000 your geohash is 1110101010101010. You index on that, then when you do a spatial search for the point nearest to 11111110,10000011 you look up key 1110101010101101 and a prefix search finds the closest value in the index is the the record you inserted earlier. Presumably then you realize there could be an even closer record at 11111111,01111111 which would have got stuck at 1011111111111111 in the index so you look there too just in case, take the closer of the two search results, and bob's your mother's brother.

[1] https://issues.apache.org/jira/browse/SOLR-2155?focusedComme... [2] http://en.wikipedia.org/wiki/Geohash

[timaelliott]

Hrm, so for a proximity search it basically has to take a combination of all potential encompassing geohashes and then do a second-pass (substantially reduced data set) using a haversine approach or something.

I suppose that might work pretty well.