add a "more like these" method

server/djrandom/frontend/search.py

 import solr
+from collections import defaultdict
 from djrandom.model.mp3 import MP3
 
 
@@ -12,3 +13,21 @@ class Searcher(object):
                                    fields='score,id', start=0, rows=n)
         for doc in results.results:
             yield doc['score'], doc['id']
+
+    def more_like_these(self, hashes):
+        """Return a set of hashes that are related to the ones provided."""
+        query_str = ' OR '.join('(id:%s)' % x for x in hashes)
+        results = self.solr.select(
+            q=query_str, fields='score,id',
+            mlt='true', mlt_fl='text', mlt_mindf=1, mlt_mintf=1)
+
+        # Parse and uniq-ify the results.
+        hashes_set = set(hashes)
+        more = defaultdict(lambda: 0)
+        for doclist in results.moreLikeThis.itervalues():
+            for doc in doclist:
+                if doc['id'] not in hashes_set:
+                    more[doc['id']] += doc['score']
+        results = more.keys()
+        results.sort(reverse=True, key=lambda x: more[x])
+        return results