endgeNGram problem

gistfile1.txt

mapping
=================
{
	"analysis": {
		"analyzer": {
		    "username_index": {
		        "tokenizer":	"keyword",
			    "filter":		["lowercase", "username_ngram"]
		    },
			"username_search": {
			    "tokenizer":	"keyword",
			    "filter":		["lowercase"]
			}
		},
		"filter": {
			"username_ngram": {
				"type":		"edgeNGram",
				"side" : 	"front",
				"min_gram":	1,
				"max_gram":	15
			}
		}
	}
}


mapping
=================
{
	"user_follow": {

		"properties": {
			"targetId": 		{ "type": "string", "store": true },
			"followerId": 		{ "type": "string", "store": true },
			"dateUpdated":	 	{ "type": "date", 	"store": true },

			"userName": { 
				"type": "multi_field",
				"fields": {
					"userName": {
                        "type":		"string",
                        "index":	"not_analyzed"
					},
					"autocomplete": {
                        "type":				"string",
                        "index_analyzer":	"username_index",
                        "search_analyzer":	"username_search"
					}
				}
			}

		}
	}
}


search:
===========
{
  "from" : 0,
  "size" : 50,
  "query" : {
    "bool" : {
      "must" : [ {
        "field" : {
          "targetId" : "51888c1b04a6a214e26a4009"
        }
      }, {
        "match" : {
          "userName.autocomplete" : {
            "query" : "brian",
            "type" : "boolean"
          }
        }
      } ]
    }
  },
  "fields" : "followerId"
}