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。

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