elasticsearch ignores boost on prefix search

boost_ignored_on_prefix_search.sh

#!/bin/sh

curl -XDELETE 'http://localhost:9200/foo'

curl -XPUT 'http://localhost:9200/foo/?pretty=true'  -d '
{
   "mappings" : {
      "bar" : {
         "properties" : {
            "title" : {
               "boost" : 2,
               "type" : "string"
            },
            "body" : {
               "type" : "string"
            }
         }
      }
   }
}
'

curl -XPOST 'http://localhost:9200/foo/bar?pretty=true'  -d '{
   "title" : "Configure",
   "body" : "Stuff about how to setup something"
}'

curl -XPOST 'http://localhost:9200/foo/bar?pretty=true'  -d '{
   "title" : "Setup",
   "body" : "Stuff about how to configure something"
}'

curl -XPOST 'http://localhost:9200/_refresh'

curl -XGET 'http://localhost:9200/foo/bar/_search?pretty=true'  -d '{
   "query" : {
      "field" : {
         "_all" : "configure"
      }
   }
}'

curl -XGET 'http://localhost:9200/foo/bar/_search?pretty=true' -d '{
   "query" : {
      "field" : {
         "_all": {
           "query": "configure*",
           "rewrite": "top_terms_10"
         }
      }
   }
}'