28、深度探秘搜索技术_实战掌握误拼写时的fuzzy模糊搜索技术

搜索的时候，可能输入的搜索文本会出现误拼写的情况

doc1: hello world
doc2: hello java

搜索：hallo world
fuzzy搜索技术 —> 自动将拼写错误的搜索文本，进行纠正，纠正以后去尝试匹配索引中的数据

POST /my_index/_bulk
{ "index": { "_id": 1 }}
{ "title": "Surprise me!"}
{ "index": { "_id": 2 }}
{ "title": "That was surprising."}
{ "index": { "_id": 3 }}
{ "title": "I wasn't surprised."}

GET /my_index/_search 
{
  "query": {
    "fuzzy": {
      "title": {
        "value": "surprize",
        "fuzziness": 2
      }
    }
  }
}

surprize —> 拼写错误 —> surprise —> s -> z
surprize —> surprise -> z -> s，纠正一个字母，就可以匹配上，所以在fuziness指定的2范围内
surprize —> surprised -> z -> s，末尾加个d，纠正了2次，也可以匹配上，在fuziness指定的2范围内
surprize —> surprising -> z -> s，去掉e，ing，3次，总共要5次，才可以匹配上，始终纠正不了
fuzzy搜索以后，会自动尝试将你的搜索文本进行纠错，然后去跟文本进行匹配
fuzziness，你的搜索文本最多可以纠正几个字母去跟你的数据进行匹配，默认如果不设置，就是2

GET /my_index/_search 
{
  "query": {
    "match": {
      "title": {
        "query": "SURPIZE ME",
        "fuzziness": "AUTO",
        "operator": "and"
      }
    }
  }
}

结果：

{
  "took" : 1,
  "timed_out" : false,
  "_shards" : {
    "total" : 1,
    "successful" : 1,
    "skipped" : 0,
    "failed" : 0
  },
  "hits" : {
    "total" : {
      "value" : 1,
      "relation" : "eq"
    },
    "max_score" : 1.8729758,
    "hits" : [
      {
        "_index" : "my_index",
        "_type" : "_doc",
        "_id" : "1",
        "_score" : 1.8729758,
        "_source" : {
          "title" : "Surprise me!"
        }
      }
    ]
  }
}

说明：案例中的 surprising 在 mapping 如下的 my_index 才能实现：

{
  "my_index" : {
    "mappings" : {
      "properties" : {
        "title" : {
          "type" : "text",
          "fields" : {
            "keyword" : {
              "type" : "keyword",
              "ignore_above" : 256
            }
          }
        }
      }
    }
  }
}

如果 my_index 的 mapping 如下：

{
  "my_index" : {
    "mappings" : {
      "properties" : {
        "title" : {
          "type" : "text",
          "analyzer" : "autocomplete",
          "search_analyzer" : "standard"
        }
      }
    }
  }
}

则如下搜索当 fuzziness = 2 时会将三条 doc 都查询出来

GET /my_index/_search 
{
  "query": {
    "fuzzy": {
      "title": {
        "value": "surprize",
        "fuzziness": 2
      }
    }
  }
}