Order Solr/sunspot search results by geo location

Question

I'd like to be able to order my search results by score and location. Each user in the DB has lat/lot and I am currently indexing:

location :coordinates do
  Sunspot::Util::Coordinates.new latlon[0], latlon[1]      
end

The model which I would performing the search against is also indexed in the same manner. Essentially what I am trying to achieve is that the results be ordered by score and then by location. So if I search for Walmart, I would like to see all Walmart's ordered by their geo proximity to my location.

I remember reading something about solr's new geo-sort but not sure if it is out of alpha and/or if sunspot has implemented a wrapper.

What would you recommend?

Answer 1

Because of the way that Sunspot calculates location types you'll need to do some extra leg work to have it sort by distance from your target as well. The way it works is that it creates a geo-hash for each point and then searches using regular fulltext search on that geo-hash. The result is that you probably won't be able to determine if a point 10km away is further than a point that is 5km away, but you'll be able to tell if a point 50km away is further than a point 1-2km away. The exact distances are arbitrary but the result is that you probably won't have as fine-grained of a result as you would like and the search acts more as a way to filter points that are within an acceptable proximity. After you have filtered your points using the built-in location search, there are three ways to accomplish what you want:

1. Upgrade to Solr 3.1 or later and upgrade your schema.xml to use the new spatial search columns. You'll then need to make custom modifications to Sunspot to create fields and orderings that work with these new data types. As far as I know these aren't available in Sunspot yet, so you'll have to make those connections on your own and you'll have to dig around in Solr to do some manual configurations.
2. Leverage the Spatial Solr Plugin. You'll have to install a new JAR into your Solr directory and you'll have to make some modifications to Sunspot, but they are relatively painless and the full instructions can be found here.
3. Leverage your DB, if your DB is also indexed on the location columns then you can use the Sunspot built-in location search to filter your results down to a reasonable sized set. You can then query the DB for those results and order them by proximity to your location using your own distance function.