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elasticsearch Analyzer 进行分词详解

蒸熟的土豆 2022-05-31 阅读 61
elasticsearchanalyzerdocker系统/运维


文章目录

  • ​​1. Anaiysis 与 Analyzer​​
  • ​​2. Analyzer 的组成​​
  • ​​3. Elastocsearch 的内置分词器​​
  • ​​3.1 使用 _analyzer Api​​
  • ​​3.1.1 直接指定 Analyzer 进行测试​​
  • ​​3.1.2 指定索引的字段进行测试​​
  • ​​3.1.3 自定义分词进行测试​​
  • ​​3.2 Standard Analyzer​​
  • ​​3.3 Simple Analyzer​​
  • ​​3.4 Whitespace Analyzer​​
  • ​​3.5 Stop Analyzer​​
  • ​​3.6 Keyword Analyzer​​
  • ​​3.7 Pattern Analyzer​​
  • ​​3.8 Language Analyzer​​
  • ​​4. 中文分词的难点​​
  • ​​4.1 ICU Analyzer​​
  • ​​4.2 更多的中文分词器​​

1. Anaiysis 与 Analyzer

  • Analysis - 文本分析是吧全文本转换成一系列的单词（term /token）的过程，也叫分词
  • Analysis 是通过 Analyzer 来实现的，可使用 Elasticesearch 内置的分析器 或者按需求定制化分析器
  • 除了在数据写入时转换词条，匹配 Query 语句时候也需要用相同的分析器会查询语句进行分析

2. Analyzer 的组成

分词器是专门处理分词的组件，Analyzer 由三部分组成

  • ​​Character Filters​​ （针对原始文本处理，例如去除 html）
  • ​​Tokenizer​​（按照规则切分为单词）
  • ​​Token Filter​​​ （将切分的单词进行加工，小写，删除 stopwords，增加同义语）
    elasticsearch Analyzer 进行分词详解_elasticsearch

3. Elastocsearch 的内置分词器

  • ​​Standard Analyzer​​ - 默认分词器，按词切分，小写处理
  • ​​Simple Analyzer​​ - 按照非字母切分（符号被过滤），小写处理
  • ​​Stop Analyzer​​ - 小写处理，停用词过滤（the ，a，is）
  • ​​Whitespace Analyzer​​ - 按照空格切分，不转小写
  • ​​Keyword Analyzer​​ - 不分词，直接将输入当做输出
  • ​​Pattern Analyzer​​ - 正则表达式，默认 \W+
  • ​​Language​​ - 提供了 30 多种常见语言的分词器
  • ​​Customer Analyzer​​ 自定义分词器

3.1 使用 _analyzer Api

3.1.1 直接指定 Analyzer 进行测试

GET _analyze
 {
   "analyzer": "standard",
   "text" : "Mastering Elasticsearch , elasticsearch in Action"
 }
 //返回结果
 {
   "tokens" : [
     {
       "token" : "mastering",
       "start_offset" : 0,
       "end_offset" : 9,
       "type" : "",
       "position" : 0
     },
     {
       "token" : "elasticsearch",
       "start_offset" : 10,
       "end_offset" : 23,
       "type" : "",
       "position" : 1
     },
     {
       "token" : "elasticsearch",
       "start_offset" : 26,
       "end_offset" : 39,
       "type" : "",
       "position" : 2
     },
     {
       "token" : "in",
       "start_offset" : 40,
       "end_offset" : 42,
       "type" : "",
       "position" : 3
     },
     {
       "token" : "action",
       "start_offset" : 43,
       "end_offset" : 49,
       "type" : "",
       "position" : 4
     }
   ]
 }

3.1.2 指定索引的字段进行测试

POST books/_analyze
{
"field": "title",
"text": "Mastering Elasticesearch"
}

3.1.3 自定义分词进行测试

POST /_analyze
  {
    "tokenizer": "standard", 
    "filter": ["lowercase"],
    "text": "Mastering Elasticesearch"
  }
  //结果返回
  {
    "tokens" : [
      {
        "token" : "mastering",
        "start_offset" : 0,
        "end_offset" : 9,
        "type" : "",
        "position" : 0
      },
      {
        "token" : "elasticesearch",
        "start_offset" : 10,
        "end_offset" : 24,
        "type" : "",
        "position" : 1
      }
    ]
  }

3.2 Standard Analyzer

elasticsearch Analyzer 进行分词详解_docker_02

#standard
GET _analyze
{
"analyzer": "standard",
"text": "2 running Quick brown-foxes leap over lazy dogs in the summer evening."
}

3.3 Simple Analyzer

elasticsearch Analyzer 进行分词详解_elasticsearch_03

#simple 去除非字母的 ：2 -  xi
GET _analyze
{
"analyzer": "simple",
"text": "2 running Quick brown-foxes leap over lazy dogs in the summer evening."
}

3.4 Whitespace Analyzer

elasticsearch Analyzer 进行分词详解_elasticsearch_04

#stop
GET _analyze
{
"analyzer": "whitespace",
"text": "2 running Quick brown-foxes leap over lazy dogs in the summer evening."
}

#return

{
  "tokens" : [
    {
      "token" : "2",
      "start_offset" : 0,
      "end_offset" : 1,
      "type" : "word",
      "position" : 0
    },
    {
      "token" : "running",
      "start_offset" : 2,
      "end_offset" : 9,
      "type" : "word",
      "position" : 1
    },
    {
      "token" : "Quick",
      "start_offset" : 10,
      "end_offset" : 15,
      "type" : "word",
      "position" : 2
    },
    {
      "token" : "brown-foxes",
      "start_offset" : 16,
      "end_offset" : 27,
      "type" : "word",
      "position" : 3
    },
    {
      "token" : "leap",
      "start_offset" : 28,
      "end_offset" : 32,
      "type" : "word",
      "position" : 4
    },
    {
      "token" : "over",
      "start_offset" : 33,
      "end_offset" : 37,
      "type" : "word",
      "position" : 5
    },
    {
      "token" : "lazy",
      "start_offset" : 38,
      "end_offset" : 42,
      "type" : "word",
      "position" : 6
    },
    {
      "token" : "dogs",
      "start_offset" : 43,
      "end_offset" : 47,
      "type" : "word",
      "position" : 7
    },
    {
      "token" : "in",
      "start_offset" : 48,
      "end_offset" : 50,
      "type" : "word",
      "position" : 8
    },
    {
      "token" : "the",
      "start_offset" : 51,
      "end_offset" : 54,
      "type" : "word",
      "position" : 9
    },
    {
      "token" : "summer",
      "start_offset" : 55,
      "end_offset" : 61,
      "type" : "word",
      "position" : 10
    },
    {
      "token" : "evening.",
      "start_offset" : 62,
      "end_offset" : 70,
      "type" : "word",
      "position" : 11
    }
  ]
}

3.5 Stop Analyzer

elasticsearch Analyzer 进行分词详解_docker_05

GET _analyze
{
"analyzer": "stop",
"text": "2 running Quick brown-foxes leap over lazy dogs in the summer evening."
}

#return
{
  "tokens" : [
    {
      "token" : "running",
      "start_offset" : 2,
      "end_offset" : 9,
      "type" : "word",
      "position" : 0
    },
    {
      "token" : "quick",
      "start_offset" : 10,
      "end_offset" : 15,
      "type" : "word",
      "position" : 1
    },
    {
      "token" : "brown",
      "start_offset" : 16,
      "end_offset" : 21,
      "type" : "word",
      "position" : 2
    },
    {
      "token" : "foxes",
      "start_offset" : 22,
      "end_offset" : 27,
      "type" : "word",
      "position" : 3
    },
    {
      "token" : "leap",
      "start_offset" : 28,
      "end_offset" : 32,
      "type" : "word",
      "position" : 4
    },
    {
      "token" : "over",
      "start_offset" : 33,
      "end_offset" : 37,
      "type" : "word",
      "position" : 5
    },
    {
      "token" : "lazy",
      "start_offset" : 38,
      "end_offset" : 42,
      "type" : "word",
      "position" : 6
    },
    {
      "token" : "dogs",
      "start_offset" : 43,
      "end_offset" : 47,
      "type" : "word",
      "position" : 7
    },
    {
      "token" : "summer",
      "start_offset" : 55,
      "end_offset" : 61,
      "type" : "word",
      "position" : 10
    },
    {
      "token" : "evening",
      "start_offset" : 62,
      "end_offset" : 69,
      "type" : "word",
      "position" : 11
    }
  ]
}

3.6 Keyword Analyzer

elasticsearch Analyzer 进行分词详解_analyzer_06

#keyword
GET _analyze
{
"analyzer": "keyword",
"text": "2 running Quick brown-foxes leap over lazy dogs in the summer evening."
}

#return
{
  "tokens" : [
    {
      "token" : "2 running Quick brown-foxes leap over lazy dogs in the summer evening.",
      "start_offset" : 0,
      "end_offset" : 70,
      "type" : "word",
      "position" : 0
    }
  ]
}

3.7 Pattern Analyzer

elasticsearch Analyzer 进行分词详解_docker_07

GET _analyze
{
"analyzer": "pattern",
"text": "2 running Quick brown-foxes leap over lazy dogs in the summer evening."
}

3.8 Language Analyzer

elasticsearch Analyzer 进行分词详解_analyzer_08

#english
GET _analyze
{
"analyzer": "english",
"text": "2 running Quick brown-foxes leap over lazy dogs in the summer evening."
}

4. 中文分词的难点

  • 中文句子，切分成一个一个次（不是一个个字）
  • 英文中，单词有自然的空格作为分隔
  • 一句中文，在不同的上下文，有不同的理解：
  1. 这个苹果，不大好吃 / 这个苹果，不大，好吃！
  2. 他说的确实在理 / 这事的确定不下来

4.1 ICU Analyzer

elasticsearch Analyzer 进行分词详解_elasticsearch_09
安装的 es 安装插件

cd /var/docker/docker-es-7.3/
    docker exec -it es7_01 bash
    bin/elasticsearch-plugin install analysis-icu
    exit
    docker exec -it es7_02 bash
    bin/elasticsearch-plugin install analysis-icu
    exit
    docker-compose restart

#icu analyzer    
POST _analyze
{
  "analyzer": "icu_analyzer",
  "text": "他说的确实在理”"
}

4.2 更多的中文分词器

IK
支持自定义词库，支持热更新分词字典
​​​ https://github.com/medcl/elasticsearch-ana…​​​ THULAC
THU Lexucal Analyzer for Chinese, 清华大学自然语言处理和社会人文计算实验室的一套中文分词器
https://github.com/microbun/elasticearch-t…

参考资料：
极客时间：Elasticsearch核心技术与实战

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