分词
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
POST _analyze
{
"analyzer": "standard",
"text": "The 2 QUICK Brown-Foxes jumped over the lazy dog's bone."
}
执行结果：
{
"tokens" : [
{
"token" : "the",
"start_offset" : 0,
"end_offset" : 3,
"type" : "",
"position" : 0
},
{
"token" : "2",
"start_offset" : 4,
"end_offset" : 5,
"type" : "",
"position" : 1
},
{
"token" : "quick",
"start_offset" : 6,
"end_offset" : 11,
"type" : "",
"position" : 2
},
{
"token" : "brown",
"start_offset" : 12,
"end_offset" : 17,
"type" : "",
"position" : 3
},
{
"token" : "foxes",
"start_offset" : 18,
"end_offset" : 23,
"type" : "",
"position" : 4
},
{
"token" : "jumped",
"start_offset" : 24,
"end_offset" : 30,
"type" : "",
"position" : 5
},
{
"token" : "over",
"start_offset" : 31,
"end_offset" : 35,
"type" : "",
"position" : 6
},
{
"token" : "the",
"start_offset" : 36,
"end_offset" : 39,
"type" : "",
"position" : 7
},
{
"token" : "lazy",
"start_offset" : 40,
"end_offset" : 44,
"type" : "",
"position" : 8
},
{
"token" : "dog's",
"start_offset" : 45,
"end_offset" : 50,
"type" : "",
"position" : 9
},
{
"token" : "bone",
"start_offset" : 51,
"end_offset" : 55,
"type" : "",
"position" : 10
}
]
}
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。
Mac下因为文件夹下有.DS_Store文件导致安装分词器有点问题，可以先启动容器后进入容器内部进行安装
docker exec -it elasticsearch /bin/bash #进入容器
/usr/share/elasticsearch/bin
./elasticsearch-plugin install https://github.com/medcl/elasticsearch-analysis-ik/releases/download/v7.4.2/elasticsearch-analysis-ik-7.4.2.zip
elasticsearch-plugin list # 列出我们所有安装的插件，看有没有ik
CentOS环境按下面安装
在 https://github.com/medcl/elasticsearch-analysis-ik/releases 找对应es版本下载
在前面安装的elasticsearch时，我们已经将elasticsearch容器的“/usr/share/elasticsearch/plugins”目录，映射到宿主机的 /mydata/elasticsearch/plugins 目录下，所以比较方便的做法就是下载“/elasticsearch-analysis-ik-7.4.2.zip”文件，然后解压到该文件夹下即可。安装完毕后，需要重启elasticsearch容器。
cd /mydata/elasticsearch/plugins
mkdir ik
cd /mydata/elasticsearch/plugins/ik
# 如果没有wget 命令先安装wget：yum -y install wget
wget https://github.com/medcl/elasticsearch-analysis-ik/releases/download/v7.4.2/elasticsearch-analysis-ik-7.4.2.zip
unzip elasticsearch-analysis-ik-7.4.2.zip
# 如果报 unzip: command not found的错误就执行下：yum install -y unzip zip
chmod -R 777 ik
docker restart elasticsearch #重启elasticsearch
docker exec -it elasticsearch /bin/bash #进入容器
cd /usr/share/elasticsearch/plugins #看有没有ik目录
cd /usr/share/elasticsearch/bin
elasticsearch-plugin -h
elasticsearch-plugin list # 列出我们所有安装的插件，看有没有ik
还可以采用如下的方式。
查看elasticsearch版本号：
[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 ~]#
进入es容器内部plugin目录：docker exec -it 容器id /bin/bash
[root@hadoop-104 ~]# docker exec -it elasticsearch /bin/bash
[root@0adeb7852e00 elasticsearch]#
[root@0adeb7852e00 elasticsearch]# pwd
/usr/share/elasticsearch
#下载ik7.4.2
[root@0adeb7852e00 elasticsearch]# wget https://github.com/medcl/elasticsearch-analysis-ik/releases/download/v7.4.2/elasticsearch-analysis-ik-7.4.2.zip
[root@0adeb7852e00 elasticsearch]# unzip elasticsearch-analysis-ik-7.4.2.zip -d ink
Archive: elasticsearch-analysis-ik-7.4.2.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/
[root@0adeb7852e00 elasticsearch]# rm -rf elasticsearch-analysis-ik-7.4.2.zip
测试分词器
使用默认分词器
GET my_index/_analyze
{
"text":"我是中国人"
}
执行结果：
{
"tokens" : [
{
"token" : "我",
"start_offset" : 0,
"end_offset" : 1,
"type" : "",
"position" : 0
},
{
"token" : "是",
"start_offset" : 1,
"end_offset" : 2,
"type" : "",
"position" : 1
},
{
"token" : "中",
"start_offset" : 2,
"end_offset" : 3,
"type" : "",
"position" : 2
},
{
"token" : "国",
"start_offset" : 3,
"end_offset" : 4,
"type" : "",
"position" : 3
},
{
"token" : "人",
"start_offset" : 4,
"end_offset" : 5,
"type" : "",
"position" : 4
}
]
}
使用ik分词器
GET my_index/_analyze
{
"analyzer": "ik_smart",
"text":"我是中国人"
}
或者
GET my_index/_analyze
{
"analyzer": "ik_max_word",
"text":"我是中国人"
}
输出结果：
{
"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
}
]
}