关于Elasticsearch 使用 MatchPhrase搜索的一些坑

  • 对分词字段检索使用的通常是match查询,对于短语查询使用的是matchphrase查询,但是并不是matchphrase可以直接对分词字段进行不分词检索(也就是业务经常说的精确匹配),下面有个例子,使用Es的请注意。
  • 某个Index下面存有如下内容
      {
          "id": "1",
          "fulltext": "亚马逊卓越有限公司诉讼某某公司"
      }
    

    其中fulltext使用ik分词器进行分词存储,使用ik分词结果如下

      "tokens": [
          {
            "token": "亚马逊",
            "start_offset": 0,
            "end_offset": 3,
            "type": "CN_WORD",
            "position": 0
          },
          {
            "token": "亚",
            "start_offset": 0,
            "end_offset": 1,
            "type": "CN_WORD",
            "position": 1
          },
          {
            "token": "马",
            "start_offset": 1,
            "end_offset": 2,
            "type": "CN_CHAR",
            "position": 2
          },
          {
            "token": "逊",
            "start_offset": 2,
            "end_offset": 3,
            "type": "CN_WORD",
            "position": 3
          },
          {
            "token": "卓越",
            "start_offset": 3,
            "end_offset": 5,
            "type": "CN_WORD",
            "position": 4
          },
          {
            "token": "卓",
            "start_offset": 3,
            "end_offset": 4,
            "type": "CN_WORD",
            "position": 5
          },
          {
            "token": "越有",
            "start_offset": 4,
            "end_offset": 6,
            "type": "CN_WORD",
            "position": 6
          },
          {
            "token": "有限公司",
            "start_offset": 5,
            "end_offset": 9,
            "type": "CN_WORD",
            "position": 7
          },
          {
            "token": "有限",
            "start_offset": 5,
            "end_offset": 7,
            "type": "CN_WORD",
            "position": 8
          },
          {
            "token": "公司",
            "start_offset": 7,
            "end_offset": 9,
            "type": "CN_WORD",
            "position": 9
          },
          {
            "token": "诉讼",
            "start_offset": 9,
            "end_offset": 11,
            "type": "CN_WORD",
            "position": 10
          },
          {
            "token": "讼",
            "start_offset": 10,
            "end_offset": 11,
            "type": "CN_WORD",
            "position": 11
          },
          {
            "token": "某某",
            "start_offset": 11,
            "end_offset": 13,
            "type": "CN_WORD",
            "position": 12
          },
          {
            "token": "某公司",
            "start_offset": 12,
            "end_offset": 15,
            "type": "CN_WORD",
            "position": 13
          },
          {
            "token": "公司",
            "start_offset": 13,
            "end_offset": 15,
            "type": "CN_WORD",
            "position": 14
          }
        ]
    

对于如上结果,如果进行matchphrase查询 “亚马逊卓越”,无法匹配出任何结果
因为对 “亚马逊卓越” 进行分词后的结果为:

    {
      "tokens": [
        {
          "token": "亚马逊",
          "start_offset": 0,
          "end_offset": 3,
          "type": "CN_WORD",
          "position": 0
        },
        {
          "token": "亚",
          "start_offset": 0,
          "end_offset": 1,
          "type": "CN_WORD",
          "position": 1
        },
        {
          "token": "马",
          "start_offset": 1,
          "end_offset": 2,
          "type": "CN_CHAR",
          "position": 2
        },
        {
          "token": "逊",
          "start_offset": 2,
          "end_offset": 3,
          "type": "CN_WORD",
          "position": 3
        },
        {
          "token": "卓越",
          "start_offset": 3,
          "end_offset": 5,
          "type": "CN_WORD",
          "position": 4
        },
        {
          "token": "卓",
          "start_offset": 3,
          "end_offset": 4,
          "type": "CN_WORD",
          "position": 5
        },
        {
          "token": "越",
          "start_offset": 4,
          "end_offset": 5,
          "type": "CN_CHAR",
          "position": 6
        }
      ]
    }

和存储的内容对比发现 原文存储中包含词语 “越有”,而查询语句中并不包含“越有”,包含的是“越”,因此使用matchphrase短语匹配失败,也就导致了无法检索出内容。
还是这个例子,换个词语进行检索,使用“亚马逊卓越有”,会发现竟然检索出来了,对“亚马逊卓越有”进行分词得到如下结果:

     {
      "tokens": [
        {
          "token": "亚马逊",
          "start_offset": 0,
          "end_offset": 3,
          "type": "CN_WORD",
          "position": 0
        },
        {
          "token": "亚",
          "start_offset": 0,
          "end_offset": 1,
          "type": "CN_WORD",
          "position": 1
        },
        {
          "token": "马",
          "start_offset": 1,
          "end_offset": 2,
          "type": "CN_CHAR",
          "position": 2
        },
        {
          "token": "逊",
          "start_offset": 2,
          "end_offset": 3,
          "type": "CN_WORD",
          "position": 3
        },
        {
          "token": "卓越",
          "start_offset": 3,
          "end_offset": 5,
          "type": "CN_WORD",
          "position": 4
        },
        {
          "token": "卓",
          "start_offset": 3,
          "end_offset": 4,
          "type": "CN_WORD",
          "position": 5
        },
        {
          "token": "越有",
          "start_offset": 4,
          "end_offset": 6,
          "type": "CN_WORD",
          "position": 6
        }
      ]
    }

注意到了吗?这里出现了越有这个词,这也就是说现在的分词结果和之前的全文分词结果完全一致了,所以matchphrash也就找到了结果。

再换一个极端点的例子,使用“越有限公司”去进行检索,你会惊讶的发现,竟然还能检索出来,对“越有限公司”进行分词,结果如下:

    {
      "tokens": [
        {
          "token": "越有",
          "start_offset": 0,
          "end_offset": 2,
          "type": "CN_WORD",
          "position": 0
        },
        {
          "token": "有限公司",
          "start_offset": 1,
          "end_offset": 5,
          "type": "CN_WORD",
          "position": 1
        },
        {
          "token": "有限",
          "start_offset": 1,
          "end_offset": 3,
          "type": "CN_WORD",
          "position": 2
        },
        {
          "token": "公司",
          "start_offset": 3,
          "end_offset": 5,
          "type": "CN_WORD",
          "position": 3
        }
      ]
    }

这个结果和原文中的结果又是完全一致(从越有之后的内容一致),所以匹配出来了结果,注意点这里有个词语“有限公司”,检索词语如果我换成了“越有限”,就会发现没有查询到内容,因为“越有限”分词结果为:

    {
      "tokens": [
        {
          "token": "越有",
          "start_offset": 0,
          "end_offset": 2,
          "type": "CN_WORD",
          "position": 0
        },
        {
          "token": "有限",
          "start_offset": 1,
          "end_offset": 3,
          "type": "CN_WORD",
          "position": 1
        }
      ]
    }

“越有”这个词是包含的,”有限”这个词语也是包含的,但是中间隔了一个“有限公司”,所以没有完全一致,也就匹配不到结果了。这时候如果我检索条件设置matchphrase的slop=1,使用“越有限”就能匹配到结果了,现在可以明白了,其实position的位置差就是slop的值,而matchphrase并不是所谓的词语拼接进行匹配,还是需要进行分词,以及position匹配的。

原文地址:https://www.cnblogs.com/eviltuzki/p/8183191.html