elasticssearch提供了CompletionSuggester查询来实现自动补全功能。这个查询会匹配以用户输入内容开头的词条并返回。为了提高补全查询效率，对于文档中字段的类型有一些约束：

+ 查询类型必须是：completion

+ 字段内容是多个补全词条形成的数组

PUT /test2
{
  "mappings": {
    "properties": {
      "title":{
        "type": "completion"   #创建字段类型的时候，只能是completion
      }
    }
  }
}

POST /test2/_doc/1
{
  "title":["Sony", "WH-1000XM3"]    #字段的内容是多词条形成的数组
}

POST test2/_doc/2
{
  "title": ["SK-II", "PITERA"]
}
POST test2/_doc/3
{
  "title": ["Nintendo", "switch"]
}

# 查询语法，自动补全
GET /test2/_search
{
  "suggest": {
    "titleSuggest": {    #查询的名称
      "text": "So",        #查询的内容
      "completion": {    #查询补全的类型
        "field": "title",    #字段类型
        "skip_duplicates": true,    #跳过重复的词条
        "size": 10         #查询的大小
      }
    }
  }
}

完成一个hotel酒店的es库创建：（创建了两个自定义的分词器）

PUT /hotel
{
  "settings": {
    "analysis": {
      "analyzer": {
        "text_anlyzer": {
          "tokenizer": "ik_max_word",
          "filter": "py"
        },
        "completion_analyzer": {
          "tokenizer": "keyword",
          "filter": "py"
        }
      },
      "filter": {
        "py": {
          "type": "pinyin",
          "keep_full_pinyin": false,
          "keep_joined_full_pinyin": true,
          "keep_original": true,
          "limit_first_letter_length": 16,
          "remove_duplicated_term": true,
          "none_chinese_pinyin_tokenize": false
        }
      }
    }
  },
  "mappings": {
    "properties": {
      "id":{
        "type": "keyword"
      },
      "name":{
        "type": "text",
        "analyzer": "text_anlyzer",
        "search_analyzer": "ik_smart",
        "copy_to": "all"
      },
      "address":{
        "type": "keyword",
        "index": false
      },
      "price":{
        "type": "integer"
      },
      "score":{
        "type": "integer"
      },
      "brand":{
        "type": "keyword",
        "copy_to": "all"
      },
      "city":{
        "type": "keyword"
      },
      "starName":{
        "type": "keyword"
      },
      "business":{
        "type": "keyword",
        "copy_to": "all"
      },
      "location":{
        "type": "geo_point"
      },
      "pic":{
        "type": "keyword",
        "index": false
      },
      "all":{
        "type": "text",
        "analyzer": "text_anlyzer",
        "search_analyzer": "ik_smart"
      },
      "suggestion":{
          "type": "completion",
          "analyzer": "completion_analyzer",
          "search_analyzer": "ik_smart"  # 使用这个为了拼音和汉字都可以使用，而不只是拼音
      }
    }
  }
}

java代码查询：

 @Test
    public void completionTest() throws IOException {
        SearchRequest request = new SearchRequest("hotel");

        request.source().suggest(new SuggestBuilder().addSuggestion(
                "suggestions",
                SuggestBuilders.completionSuggestion("suggestion")
                        .prefix("火")
                        .size(10)
                        .skipDuplicates(true)
        ));

        SearchResponse response = client.search(request, RequestOptions.DEFAULT);

        Suggest suggest = response.getSuggest();
        CompletionSuggestion suggestions = suggest.getSuggestion("suggestions");
        List<CompletionSuggestion.Entry.Option> options = suggestions.getOptions();
        for (CompletionSuggestion.Entry.Option option : options) {
            String string = option.getText().string();
            System.out.println(string);
        }
    }