Elasticsearch 自带一种自动补全类型 completion
这种类型不在mapping文档里面有点坑。

先直接上例子。

建立 index,把我们要自动补全的字段设置为 completion 类型
或者直接设置为子类型

PUT /blogs_completion/
{
  "mappings": {
    "tech": {
      "properties": {
        "body": {
          "type": "completion"
        }
      }
    }
  }
}

// 设置为子类型
PUT /blogs_completion/
{
  "mappings": {
    "properties": {
      "body": {
        "type": "text",
        "fields": {
          "suggest":{
            "type":"completion"
          },
          "keyword":{
            "type":"keyword"
          }
        }
      }
    }
  }
}



//填充测试用例inter开头文本，和inter 的变形单词inber等
POST _bulk/?refresh=true
{ "index" : { "_index" : "blogs_completion", "_type" : "tech" } }
{ "body": "interface test1"}
{ "index" : { "_index" : "blogs_completion", "_type" : "tech" } }
{ "body": "interf test2"}
{ "index" : { "_index" : "blogs_completion", "_type" : "tech" } }
{ "body": "inter test3"}
{ "index" : { "_index" : "blogs_completion", "_type" : "tech" } }
{ "body": "inber test"}
{ "index" : { "_index" : "blogs_completion", "_type" : "tech" } }
{ "body": "sinter test"}

// 使用带模糊匹配的 completion suggester 查询

POST blogs_completion/_search?pretty
{ "size": 0,
  "suggest": {
    "blog-suggest": {
      "prefix": "inter",
      "completion": {
        "size":"5",
        "field": "body",
        "fuzzy" : {
            "fuzziness" : 2
        }
      }
    }
  }
}

// 结果

{
  "took" : 1,
  "timed_out" : false,
  "_shards" : {
    "total" : 5,
    "successful" : 5,
    "skipped" : 0,
    "failed" : 0
  },
  "hits" : {
    "total" : 0,
    "max_score" : 0.0,
    "hits" : [ ]
  },
  "suggest" : {
    "blog-suggest" : [
      {
        "text" : "inter",
        "offset" : 0,
        "length" : 5,
        "options" : [
          {
            "text" : "inter test",
            "_index" : "blogs_completion",
            "_type" : "tech",
            "_id" : "Fd_wOHABW8nrxgV2Ej6u",
            "_score" : 3.0,
            "_source" : {
              "body" : "inter test"
            }
          },
          {
            "text" : "interf test",
            "_index" : "blogs_completion",
            "_type" : "tech",
            "_id" : "FN_wOHABW8nrxgV2Ej6u",
            "_score" : 3.0,
            "_source" : {
              "body" : "interf test"
            }
          },
          {
            "text" : "interface test",
            "_index" : "blogs_completion",
            "_type" : "tech",
            "_id" : "E9_wOHABW8nrxgV2Ej6u",
            "_score" : 3.0,
            "_source" : {
              "body" : "interface test"
            }
          },
          {
            "text" : "inber test",
            "_index" : "blogs_completion",
            "_type" : "tech",
            "_id" : "HN__OHABW8nrxgV2lD4C",
            "_score" : 2.0,
            "_source" : {
              "body" : "inber test"
            }
          }
        ]
      }
    ]
  }
}

概述：

Elasticsearch 自带 suggest query 的功能，作为自动补全和查询建议的工具，称为 suggester

分为四种:

1. Term suggester
2. Phrase Suggester
3. Completion Suggester
4. Context Suggester

Completion Suggester 已经可以满足我们一般的带模糊查询的前缀自动补全功能，
如果要做更复杂的自动补全，可以结合 term suggester 和 phrase suggester 和 completion,同时查询，合并结果，得到更复杂的结果

一般详细文档：

https://blog.csdn.net/wwd0501/article/details/80595201

官方详情查考

https://www.elastic.co/guide/en/elasticsearch/reference/current/search-suggesters.html#context-suggester