一个tokenizer（分词器）接收一个字符流，将之分割为独立的tokens（词元，通常是独立的单词），然后输出tokens流。例如：whitespace tokenizer遇到空白字符时分割文本。它会将文本“Quick brown fox!”分割为[Quick,brown,fox!]。该tokenizer（分词器）还负责记录各个terms(词条)的顺序或position位置（用于phrase短语和word proximity词近邻查询），以及term（词条）所代表的原始word（单词）的start（起始）和end（结束）的character offsets（字符串偏移量）（用于高亮显示搜索的内容）。

elasticsearch提供了很多内置的分词器，可以用来构建custom analyzers（自定义分词器）。

关于分词器： https://www.elastic.co/guide/en/elasticsearch/reference/7.6/analysis.html

使用内置分词器

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POST _analyze
{
  "analyzer": "standard",
  "text": "The 2 QUICK Brown-Foxes jumped over the lazy dog's bone."
}

执行结果：

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{
  "tokens" : [
    {
      "token" : "the",
      "start_offset" : 0,
      "end_offset" : 3,
      "type" : "<ALPHANUM>",
      "position" : 0
    },
    {
      "token" : "2",
      "start_offset" : 4,
      "end_offset" : 5,
      "type" : "<NUM>",
      "position" : 1
    },
    {
      "token" : "quick",
      "start_offset" : 6,
      "end_offset" : 11,
      "type" : "<ALPHANUM>",
      "position" : 2
    },
    {
      "token" : "brown",
      "start_offset" : 12,
      "end_offset" : 17,
      "type" : "<ALPHANUM>",
      "position" : 3
    },
    {
      "token" : "foxes",
      "start_offset" : 18,
      "end_offset" : 23,
      "type" : "<ALPHANUM>",
      "position" : 4
    },
    {
      "token" : "jumped",
      "start_offset" : 24,
      "end_offset" : 30,
      "type" : "<ALPHANUM>",
      "position" : 5
    },
    {
      "token" : "over",
      "start_offset" : 31,
      "end_offset" : 35,
      "type" : "<ALPHANUM>",
      "position" : 6
    },
    {
      "token" : "the",
      "start_offset" : 36,
      "end_offset" : 39,
      "type" : "<ALPHANUM>",
      "position" : 7
    },
    {
      "token" : "lazy",
      "start_offset" : 40,
      "end_offset" : 44,
      "type" : "<ALPHANUM>",
      "position" : 8
    },
    {
      "token" : "dog's",
      "start_offset" : 45,
      "end_offset" : 50,
      "type" : "<ALPHANUM>",
      "position" : 9
    },
    {
      "token" : "bone",
      "start_offset" : 51,
      "end_offset" : 55,
      "type" : "<ALPHANUM>",
      "position" : 10
    }
  ]
}

1、安装ik分词器

所有的语言分词，默认使用的都是“Standard Analyzer”，但是这些分词器针对于中文的分词，并不友好。为此需要安装中文的分词器。

注意：不能用默认elasticsearch-plugin install xxx.zip 进行自动安装

https://github.com/medcl/elasticsearch-analysis-ik/releases/download 对应es版本安装

（1）查看elasticsearch版本号：
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[root@hadoop-104 ~]# curl http://localhost:9200
{
  "name" : "0adeb7852e00",
  "cluster_name" : "elasticsearch",
  "cluster_uuid" : "9gglpP0HTfyOTRAaSe2rIg",
  "version" : {
    "number" : "7.6.2",      #版本号为7.6.2
    "build_flavor" : "default",
    "build_type" : "docker",
    "build_hash" : "ef48eb35cf30adf4db14086e8aabd07ef6fb113f",
    "build_date" : "2020-03-26T06:34:37.794943Z",
    "build_snapshot" : false,
    "lucene_version" : "8.4.0",
    "minimum_wire_compatibility_version" : "6.8.0",
    "minimum_index_compatibility_version" : "6.0.0-beta1"
  },
  "tagline" : "You Know, for Search"
}
[root@hadoop-104 ~]#
（2）进入es容器内部plugin目录
  • docker exec -it 容器id /bin/bash
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[root@hadoop-104 ~]# docker exec -it elasticsearch /bin/bash
[root@0adeb7852e00 elasticsearch]# 
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[root@0adeb7852e00 elasticsearch]# pwd
/usr/share/elasticsearch
#下载ik7.6.2
[root@0adeb7852e00 elasticsearch]# wget https://github.com/medcl/elasticsearch-analysis-ik/releases/download/v7.6.2/elasticsearch-analysis-ik-7.6.2.zip
  • unzip 下载的文件
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[root@0adeb7852e00 elasticsearch]# unzip elasticsearch-analysis-ik-7.6.2.zip -d ink
Archive:  elasticsearch-analysis-ik-7.6.2.zip
   creating: ik/config/
  inflating: ik/config/main.dic      
  inflating: ik/config/quantifier.dic  
  inflating: ik/config/extra_single_word_full.dic  
  inflating: ik/config/IKAnalyzer.cfg.xml  
  inflating: ik/config/surname.dic   
  inflating: ik/config/suffix.dic    
  inflating: ik/config/stopword.dic  
  inflating: ik/config/extra_main.dic  
  inflating: ik/config/extra_stopword.dic  
  inflating: ik/config/preposition.dic  
  inflating: ik/config/extra_single_word_low_freq.dic  
  inflating: ik/config/extra_single_word.dic  
  inflating: ik/elasticsearch-analysis-ik-7.6.2.jar  
  inflating: ik/httpclient-4.5.2.jar  
  inflating: ik/httpcore-4.4.4.jar   
  inflating: ik/commons-logging-1.2.jar  
  inflating: ik/commons-codec-1.9.jar  
  inflating: ik/plugin-descriptor.properties  
  inflating: ik/plugin-security.policy  
[root@0adeb7852e00 elasticsearch]#
#移动到plugins目录下
[root@0adeb7852e00 elasticsearch]# mv ik plugins/
  • rm -rf *.zip
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[root@0adeb7852e00 elasticsearch]# rm -rf elasticsearch-analysis-ik-7.6.2.zip

确认是否安装好了分词器

2、测试分词器

​ 接下来使用ik分词器对中文语句进行测试。

使用默认分词器给中文分词

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GET my_index/_analyze
{
   "text":"我是中国人"
}

执行结果：

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{
  "tokens" : [
    {
      "token" : "我",
      "start_offset" : 0,
      "end_offset" : 1,
      "type" : "<IDEOGRAPHIC>",
      "position" : 0
    },
    {
      "token" : "是",
      "start_offset" : 1,
      "end_offset" : 2,
      "type" : "<IDEOGRAPHIC>",
      "position" : 1
    },
    {
      "token" : "中",
      "start_offset" : 2,
      "end_offset" : 3,
      "type" : "<IDEOGRAPHIC>",
      "position" : 2
    },
    {
      "token" : "国",
      "start_offset" : 3,
      "end_offset" : 4,
      "type" : "<IDEOGRAPHIC>",
      "position" : 3
    },
    {
      "token" : "人",
      "start_offset" : 4,
      "end_offset" : 5,
      "type" : "<IDEOGRAPHIC>",
      "position" : 4
    }
  ]
}

使用ik分词器的ik_smart

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GET my_index/_analyze
{
   "analyzer": "ik_smart", 
   "text":"我是中国人"
}

输出结果：

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{
  "tokens" : [
    {
      "token" : "我",
      "start_offset" : 0,
      "end_offset" : 1,
      "type" : "CN_CHAR",
      "position" : 0
    },
    {
      "token" : "是",
      "start_offset" : 1,
      "end_offset" : 2,
      "type" : "CN_CHAR",
      "position" : 1
    },
    {
      "token" : "中国人",
      "start_offset" : 2,
      "end_offset" : 5,
      "type" : "CN_WORD",
      "position" : 2
    }
  ]
}

使用ik分词器的ik_max_word

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GET my_index/_analyze
{
   "analyzer": "ik_max_word", 
   "text":"我是中国人"
}

输出结果：

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{
  "tokens" : [
    {
      "token" : "我",
      "start_offset" : 0,
      "end_offset" : 1,
      "type" : "CN_CHAR",
      "position" : 0
    },
    {
      "token" : "是",
      "start_offset" : 1,
      "end_offset" : 2,
      "type" : "CN_CHAR",
      "position" : 1
    },
    {
      "token" : "中国人",
      "start_offset" : 2,
      "end_offset" : 5,
      "type" : "CN_WORD",
      "position" : 2
    },
    {
      "token" : "中国",
      "start_offset" : 2,
      "end_offset" : 4,
      "type" : "CN_WORD",
      "position" : 3
    },
    {
      "token" : "国人",
      "start_offset" : 3,
      "end_offset" : 5,
      "type" : "CN_WORD",
      "position" : 4
    }
  ]
}

3、自定义词库
  • 修改/usr/share/elasticsearch/plugins/ik/config中的IKAnalyzer.cfg.xml
    /usr/share/elasticsearch/plugins/ik/config
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<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE properties SYSTEM "http://java.sun.com/dtd/properties.dtd">
<properties>
	<comment>IK Analyzer 扩展配置</comment>
	<!--用户可以在这里配置自己的扩展字典 -->
	<entry key="ext_dict"></entry>
	 <!--用户可以在这里配置自己的扩展停止词字典-->
	<entry key="ext_stopwords"></entry>
	<!--用户可以在这里配置远程扩展字典 -->
	<entry key="remote_ext_dict">http://192.168.137.14/es/fenci.txt</entry> 
	<!--用户可以在这里配置远程扩展停止词字典-->
	<!-- <entry key="remote_ext_stopwords">words_location</entry> -->
</properties>

原来的xml

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<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE properties SYSTEM "http://java.sun.com/dtd/properties.dtd">
<properties>
	<comment>IK Analyzer 扩展配置</comment>
	<!--用户可以在这里配置自己的扩展字典 -->
	<entry key="ext_dict"></entry>
	 <!--用户可以在这里配置自己的扩展停止词字典-->
	<entry key="ext_stopwords"></entry>
	<!--用户可以在这里配置远程扩展字典 -->
	<!-- <entry key="remote_ext_dict">words_location</entry> -->
	<!--用户可以在这里配置远程扩展停止词字典-->
	<!-- <entry key="remote_ext_stopwords">words_location</entry> -->
</properties>

修改完成后，需要重启elasticsearch容器，否则修改不生效。

更新完成后，es只会对于新增的数据用更新分词。历史数据是不会重新分词的。如果想要历史数据重新分词，需要执行：

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POST my_index/_update_by_query?conflicts=proceed

http://192.168.137.14/es/fenci.txt，这个是nginx上资源的访问路径

在运行下面实例之前，需要安装nginx（安装方法见安装nginx），然后创建“fenci.txt”文件，内容如下：

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echo "樱桃萨其马，带你甜蜜入夏" > /mydata/nginx/html/fenci.txt

测试效果：

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GET my_index/_analyze
{
   "analyzer": "ik_max_word", 
   "text":"樱桃萨其马，带你甜蜜入夏"
}

输出结果：

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{
  "tokens" : [
    {
      "token" : "樱桃",
      "start_offset" : 0,
      "end_offset" : 2,
      "type" : "CN_WORD",
      "position" : 0
    },
    {
      "token" : "萨其马",
      "start_offset" : 2,
      "end_offset" : 5,
      "type" : "CN_WORD",
      "position" : 1
    },
    {
      "token" : "带你",
      "start_offset" : 6,
      "end_offset" : 8,
      "type" : "CN_WORD",
      "position" : 2
    },
    {
      "token" : "甜蜜",
      "start_offset" : 8,
      "end_offset" : 10,
      "type" : "CN_WORD",
      "position" : 3
    },
    {
      "token" : "入夏",
      "start_offset" : 10,
      "end_offset" : 12,
      "type" : "CN_WORD",
      "position" : 4
    }
  ]
}