当第一个字母拼写错误时,来自elasticsearch短语suggester的意外结果

我正在使用Elasticsearch短语Suggester来纠正用户的拼写错误。一切都如我所料,除非用户输入一个查询,它的第一个字母拼写错误。在这种情况下,短语suggester不返回任何内容或返回意外结果。

我的文档和查询与 phrase suggester :

POST test/test?refresh=true
{"title": "noble warriors"}
POST test/test?refresh=true
{"title": "nobel prize"}

    POST test/_search
{
  "suggest": {
    "text": "noble prize",
    "simple_phrase": {
      "phrase": {
        "field": "title.trigram",
        "size": 1,
        "gram_size": 3,
        "direct_generator": [ {
          "field": "title.trigram",
          "suggest_mode": "always"
        } ],
        "highlight": {
          "pre_tag": "<em>",
          "post_tag": "</em>"
        }
      }
    }
  }
}

   {
  "_shards": ...
  "hits": ...
  "timed_out": false,
  "took": 3,
  "suggest": {
    "simple_phrase" : [
      {
        "text" : "mobel prize",
        "offset" : 0,
        "length" : 11,
        "options" : []
      }
    ]
  }
}

第4个字母拼写错误的示例:

{
  "_shards": ...
  "hits": ...
  "timed_out": false,
  "took": 3,
  "suggest": {
    "simple_phrase" : [
      {
        "text" : "noble prize",
        "offset" : 0,
        "length" : 11,
        "options" : [ {
          "text" : "nobel prize",
          "highlighted": "<em>nobel</em> prize",
          "score" : 0.5962314
        }]
      }
    ]
  }
}