Elasticsearch 2.2 Java API最小字段长度

我想用以下代码搜索名字和姓氏：

TransportClient client = elasticSearchProvider.getClient();
    SearchRequestBuilder requestBuilder = client.prepareSearch("migranthire").setTypes("refugee").setSearchType(SearchType.QUERY_THEN_FETCH);


    //Queries
    BoolQueryBuilder queryBuilder = new BoolQueryBuilder();
    queryBuilder.must(QueryBuilders.queryStringQuery(query + "*"));
    queryBuilder.should(QueryBuilders.multiMatchQuery(query + "", "first_name", "last_name").boost(2).operator(MatchQueryBuilder.Operator.AND));

    if (talent != null && talent == 0) {
        queryBuilder.must(QueryBuilders.queryStringQuery(0 + "").field("talent"));
    }
    //Active ones
    queryBuilder.must(QueryBuilders.queryStringQuery(1 + "").field("active"));


    requestBuilder.setQuery(queryBuilder);
    requestBuilder.setFrom(start);
    requestBuilder.setSize(limit);
    requestBuilder.setFetchSource(new String[]{"id"}, null);

我唯一找不到的是->如何过滤搜索结果，其中first_name和last_name是空的，或者该字段的长度是多少