ES ik分詞器使用技巧

match查詢會將查詢詞分詞，而後對分詞的結果進行term查詢。

而後默認是將每一個分詞term查詢以後的結果求交集，因此只要分詞的結果可以命中，某條數據就能夠被查詢出來，而分詞是在新建索引時指定的，只有text類型的數據才能設置分詞策略。

新建索引，並指定分詞策略：

PUT mail_test3
{
  "settings": {
    "index": {
      "refresh_interval": "30s",
      "number_of_shards": "1",
      "number_of_replicas": "0"
    }
  },
  "mappings": {
    "default": {
      "_all": {
        "enabled": false
      },
      "_source": {
        "enabled": true
      },
      "properties": {
        "addressTude": {
          "type": "text",
          "analyzer": "ik_max_word",
          "search_analyzer": "ik_smart",
          "copy_to": [
            "commonText"
          ],
          "fielddata": true
        },
        "captureTime": {
          "type": "long"
        },
        "commonText": {
          "type": "text",
          "analyzer": "ik_max_word",
          "search_analyzer": "ik_smart",
          "fielddata": true
        },
        "commonNum":{
          "type": "text",
          "analyzer": "ik_max_word",
          "search_analyzer": "ik_smart",
          "fielddata": true
        },
        "imsi": {
          "type": "keyword",
          "copy_to": ["commonNum"]
        },
        "uuid": {
          "type": "keyword"
        }
      }
    }
  }
}

analyzer 指的是在建索引時的分詞策略，search_analyzer 指的是在查詢時的分詞策略。ik分詞器還有一種ik_smart 的分詞策略，能夠比較兩種分詞策略的差異：

ik_smart分詞策略：

GET mail_test3/_analyze
{
  "analyzer": "ik_smart",
  "text": "湖南省湘潭市江山路96號-11-8"
}

結果：

{
  "tokens": [
    {
      "token": "湖南省",
      "start_offset": 0,
      "end_offset": 3,
      "type": "CN_WORD",
      "position": 0
    },
    {
      "token": "湘潭市",
      "start_offset": 3,
      "end_offset": 6,
      "type": "CN_WORD",
      "position": 1
    },
    {
      "token": "江",
      "start_offset": 6,
      "end_offset": 7,
      "type": "CN_CHAR",
      "position": 2
    },
    {
      "token": "山路",
      "start_offset": 7,
      "end_offset": 9,
      "type": "CN_WORD",
      "position": 3
    },
    {
      "token": "96號",
      "start_offset": 9,
      "end_offset": 12,
      "type": "TYPE_CQUAN",
      "position": 4
    },
    {
      "token": "11-8",
      "start_offset": 13,
      "end_offset": 17,
      "type": "LETTER",
      "position": 5
    }
  ]
}

ik_max_word分詞策略：

GET mail_test1/_analyze
{
  "analyzer": "ik_max_word",
  "text": "湖南省湘潭市江山路96號-11-8"
}

分詞結果：

{
  "tokens": [
    {
      "token": "湖南省",
      "start_offset": 0,
      "end_offset": 3,
      "type": "CN_WORD",
      "position": 0
    },
    {
      "token": "湖南",
      "start_offset": 0,
      "end_offset": 2,
      "type": "CN_WORD",
      "position": 1
    },
    {
      "token": "省",
      "start_offset": 2,
      "end_offset": 3,
      "type": "CN_CHAR",
      "position": 2
    },
    {
      "token": "湘潭市",
      "start_offset": 3,
      "end_offset": 6,
      "type": "CN_WORD",
      "position": 3
    },
    {
      "token": "湘潭",
      "start_offset": 3,
      "end_offset": 5,
      "type": "CN_WORD",
      "position": 4
    },
    {
      "token": "市",
      "start_offset": 5,
      "end_offset": 6,
      "type": "CN_CHAR",
      "position": 5
    },
    {
      "token": "江山",
      "start_offset": 6,
      "end_offset": 8,
      "type": "CN_WORD",
      "position": 6
    },
    {
      "token": "山路",
      "start_offset": 7,
      "end_offset": 9,
      "type": "CN_WORD",
      "position": 7
    },
    {
      "token": "96",
      "start_offset": 9,
      "end_offset": 11,
      "type": "ARABIC",
      "position": 8
    },
    {
      "token": "號",
      "start_offset": 11,
      "end_offset": 12,
      "type": "COUNT",
      "position": 9
    },
    {
      "token": "11-8",
      "start_offset": 13,
      "end_offset": 17,
      "type": "LETTER",
      "position": 10
    },
    {
      "token": "11",
      "start_offset": 13,
      "end_offset": 15,
      "type": "ARABIC",
      "position": 11
    },
    {
      "token": "8",
      "start_offset": 16,
      "end_offset": 17,
      "type": "ARABIC",
      "position": 12
    }
  ]
}

ik_max_word分詞器的分詞結果更多，分詞的粒度更細，而ik_smart的分詞結果粒度更粗，但較爲智能。通常的策略是創建索引使用ik_max_word，查詢時使用ik_smart，這樣就能儘量多的查到結果，並且上文提到，match查詢最終是轉化爲term查詢，所以只要某個分詞結果命中，結果中就會有該條數據。

若是對搜索結果的精度較高，能夠在查詢中加入operator參數，而後讓分詞結果的每一個term查詢結果之間求交集，這樣能儘量地提升精度。

這裏的operator設置爲or和and的差異較大，能夠測試進行比較：

GET mail_test3/_search
{
  "query": {
    "match": {
      "commonText": {
         "query": "湖北省宜昌市天台東二街",
         "operator": "and"
      }
    }
  }
}