Order Solr results by degrees of friendship

I am currently using Solr 1.4 (soon to upgrade to 3.3). The friendship table is pretty standard:

id | follower_id | user_id 

I would like to perform a regular keyword solr search and order the results by degrees of separation as well as the standard score ordering. From the result set, given the keyword matche开发者_如何学JAVAd any of my immediate friends, they would show up first. Secondly would be the friends of my friends, and thirdly friends by 3rd degree of separation. All other results would come after.

I am pretty sure Solr doesn't offer any 'pre-baked' way of doing this therefore I would likely have to do a join on MySQL to properly order the results. Curious if anyone has done this before and/or has some insights.

It's simply not possible in Solr. However, if you aren't too restricted and could use another platform for this, consider neo4j?

This "connections" and degrees is exactly where Neo4j steps in.

http://neo4j.org/

One way might be to create fields like degree_1, degree_2 etc. and store the list of friends at degree x in the field degree_x. Then you could fire multiple queries - the first restricting the results to those who have you in degree_1, the second restricting the results to those who have you in degree_2 and so on.

It is a bit complicated, but the only solution I could think of using Solr.

I haven't represented a graph in solr before, but I think at a high level, this is what you could do. First, represent people as nodes and the social network as a graph in the database. Implement transitive closure function in sql to allow you to walk the graph. Then you would index the result into solr with the social network info stored into payloads, for example.

I was able to achieve this by performing multiple queries and with the scope "with" to restrict to the id's of colleagues, 2nd and 3rd degree colleagues, using the id's and using mysql to do the select.

@search_1 = perform_search(1, options)
@search_2 = perform_search(2, options)

if degree == 1
  with(:id).any_of(options[:colleague_ids])
elsif degree == 2
  with(:id).any_of(options[:second_degree_colleagues])
end

It's kinda of a dirty solution as I have to perform multiple solr queries, but until I can use dynamic field sorting options (solr 3.3, not currently supported by sunspot) I really don't know any other way to achieve this.