Elasticsearch Analysis 分析器

• Analysis —文本分析是把全文本转换一系列单词（term/token)的过程，也叫分词
• Analysis是通过Analyzer来实现的
  • 可使用 Elasticsearch 内置的分析器/或者按需定制化分析器
  • 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对查询语句进行分析

Analyzer 分析器组成

分词器是专门处理分词的组件，由三部分组成

• Character Filters(针对原始文本处理，例如去除HTML)
• Tokenizer 安装规则分词
• Token Filter 将切分的单词进行加工、小写，删除stopwords，增加同义词

使用 Analyzer 分析器进行分词

analyzer 分析器:

• 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，直接将输入当作输出
• Patter Analyzer – 正则表达式，默认 \W+ (非字符分隔)
• Language – 提供了30多种常见语言的分词器

查看不同 analyzer 分析器的效果

standard 标准分析器(默认)

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

=================== 结果 V ===================
{
  "tokens" : [
    {
      "token" : "2",
      "start_offset" : 0,
      "end_offset" : 1,
      "type" : "<NUM>",
      "position" : 0
    },
    {
      "token" : "running",
      "start_offset" : 2,
      "end_offset" : 9,
      "type" : "<ALPHANUM>",
      "position" : 1
    },
    ......
    {
      "token" : "evening",
      "start_offset" : 62,
      "end_offset" : 69,
      "type" : "<ALPHANUM>",
      "position" : 12
    }
  ]
}

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

=================== 结果 V ===================
{
  "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" : "evening",
      "start_offset" : 62,
      "end_offset" : 69,
      "type" : "word",
      "position" : 11
    }
  ]
}

更多分词器例子

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


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


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

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

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


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


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


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


POST _analyze
{
  "analyzer": "icu_analyzer",
  "text": "这个苹果不大好吃"
}

需要注意的是, icu_analyzer 分析器; 包括 ik 分析器; 并非 Elasticsearch 7.8.0 自带分析器.

需要执行命令:./bin/elasticsearch-plugin install analysis-icu 自行安装并重启 elasticsearch 才能使用

更多中文分词

ik

支持自定义词库，支持热更新分词
https://gitee.com/mirrors/elasticsearch-analysis-ik?_from=gitee_search

THULAC

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://gitee.com/puremilk/THULAC-Python?_from=gitee_search

相关阅读

• https://www.elastic.co/guide/en/elasticsearch/reference/7.1/indices-analyze.html
• https://www.elastic.co/guide/en/elasticsearch/reference/current/analyzer-anatomy.html