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字符过滤器
注意:字符过滤器用于在将字符流传递给分词器之前对其进行预处理
html_strip HTML元素替换过滤器
此过滤器会替换掉HTML标签,且会转换HTML实体 如:& 会被替换为 &。
{"tokenizer": "keyword","char_filter": ["html_strip"],"text": "<p>I'm so <b>happy</b>!</p>"
}
解析结果:
[ \nI'm so happy!\n ]
因为是 p 标签,所以有前后的换行符。如果使用<span>标签就不会有换行符了。
可配参数说明
- escaped_tags
(可选,字符串数组)不包含尖括号 ( < >) 的 HTML 元素数组。当从文本中剥离 HTML 时,过滤器会跳过这些 HTML 元素。例如,设置 [ “p” ] 将会跳过 <p> HTML 元素。
自定义字符过滤器
{"settings": {"analysis": {"analyzer": {"my_analyzer": {"tokenizer": "keyword","char_filter": ["my_custom_html_strip_char_filter"]}},"char_filter": {"my_custom_html_strip_char_filter": {"type": "html_strip","escaped_tags": ["b"]}}}}
}
自定义字符过滤器 my_custom_html_strip_char_filter ,以 html_strip 过滤器为基础,设置了跳过 b 标签不过滤。
mapping 键值替换过滤器
配置键和值的映射,每当遇到与键相同的字符串时,它就会用与该键关联的值替换它们
{"tokenizer": "keyword","char_filter": [{"type": "mapping","mappings": ["0 => 零","1 => 壹","2 => 贰","3 => 叁","4 => 肆","5 => 伍","6 => 陆","7 => 柒","8 => 捌","9 => 玖"]}],"text": "9527就是你的终身代号"
}
解析结果:
{"tokens": [{"token": "玖伍贰柒就是你的终身代号","start_offset": 0,"end_offset": 12,"type": "word","position": 0}]
}
可配参数说明
- mappings
(必需*,字符串数组)映射数组,每个元素的形式为key => value. - mappings_path
(必需*,字符串)包含映射的文件的路径key => value。
此路径必须是绝对路径或相对于config位置的路径,并且文件必须是 UTF-8 编码的。文件中的每个映射必须用换行符分隔。
以上两个参数二选一即可。
pattern_replace 正则替换过滤器
{"tokenizer": "keyword","char_filter": [{"type": "pattern_replace","pattern": "(\\d{3})(\\d{4})(\\d{4})","replacement":"$1****$3"}],"text": "13199838273"
}
解析结果:
{"tokens": [{"token": "131****8273","start_offset": 0,"end_offset": 11,"type": "word","position": 0}]
}
看到结果你就知道我们示例的作用了,关于写法可以看看可配参数的说明。
可配参数说明
- pattern
必需,Java正则表达式。 - replacement
替换字符串,用 $1…$9来表示正则表达式匹配的内容。注意,我们的示例中每一个正则匹配都用了()括号扩起来。 - flags
Java 正则表达式标志。
常用分词器
分析器只能配置一个分词器,所以很多分词器的名称和分析器的名称是一致的
标准分词器
standard词器提供基于语法的分词(基于 Unicode 文本分割算法)并且适用于大多数语言。
POST _analyze
{"tokenizer": "standard","text": "The 2 QUICK Brown-Foxes jumped over the lazy dog's bone."
}
解析结果:
[ The, 2, QUICK, Brown, Foxes, jumped, over, the, lazy, dog's, bone ]
如果仔细对比,你还是能发现和 standard 分析器处理结果的区别的。
我们来试试中文
{"tokenizer": "standard","text": "我是中国人"
}
解析结果:
[我,是,中,国,人]
分词是分词了,但是貌似不符合我们的要求,关于中文的分词我们后面再说。
可配参数说明
- max_token_length
单个词语的最大长度。如果词语长度超过该长度,则按max_token_length间隔将其拆分。默认为255。
自定义分词器
PUT /person1
{"settings": {"analysis": {"analyzer": {"my_analyzer": {"tokenizer": "my_tokenizer"}},"tokenizer": {"my_tokenizer": {"type": "standard","max_token_length": 5}}}}
}
注意配置参数:我们配置了一个自定义的分词器 my_tokenizer ,以 standard 为基础类型,然后配置了一个自定义的分析器 my_analyzer,设置该分析器的分词器为 my_tokenizer 。
letter 字母分词器
只要遇到不是字母的字符,分词器就会将文本分解。它对大多数欧洲语言都做得很好,但对一些亚洲语言来说就很糟糕,因为在这些语言中单词没有用空格分隔。
POST _analyze
{"tokenizer": "letter","text": "The 2 QUICK Brown-Foxes jumped over the lazy dog's bone."
}
解析结果:
[ The, QUICK, Brown, Foxes, jumped, over, the, lazy, dog, s, bone]
lowercase 小写分词器
其作用和 letter 分词器一样,只是会将字母转换为小写。此处我们就不贴示例了。
classic 经典分词器
适用于英语文档。此分词器具有对首字母缩写词、公司名称、电子邮件地址和 Internet 主机名进行特殊处理的启发式方法。然而,这些规则并不总是有效,分词器对除英语以外的大多数语言都不能很好地工作
POST _analyze
{"tokenizer": "standard","text": "The 2 QUICK Brown-Foxes jumped over the lazy dog's bone. email: abc@cormm.com"
}
解析结果:
{"tokens": [{"token": "The","start_offset": 0,"end_offset": 3,"type": "<ALPHANUM>","position": 0},{"token": "2","start_offset": 4,"end_offset": 5,"type": "<ALPHANUM>","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": "<APOSTROPHE>","position": 9},{"token": "bone","start_offset": 51,"end_offset": 55,"type": "<ALPHANUM>","position": 10},{"token": "email","start_offset": 57,"end_offset": 62,"type": "<ALPHANUM>","position": 11},{"token": "abc@cormm.com","start_offset": 64,"end_offset": 77,"type": "<EMAIL>","position": 12}]
}
关于与 standard 分词器的区别,可以自行验证一下。
可配参数说明
- max_token_length
单个词语的最大长度。如果词语长度超过该长度,则按max_token_length间隔将其拆分。默认为255。
path_hierarchy 路径层次分词器
POST _analyze
{"tokenizer": "path_hierarchy","text": "/one/two/three"
}
解析结果:
[ /one, /one/two, /one/two/three ]
可配参数说明
- delimiter
用作路径分隔符的字符。默认为 / - replacement
用于分隔符的可选替换字符。默认为delimiter. - buffer_size
单次读取到术语缓冲区的字符数。默认为1024. 术语缓冲区将按此大小增长,直到所有文本都被消耗掉。建议不要更改此设置。 - reverse:是否反转,默认为false。
- skip
要跳过的初始标记数。默认为0.
示例2
拆分 - 字符,并将它们替换为 / 并跳过前两个标记
PUT /person1
{"settings": {"analysis": {"analyzer": {"my_analyzer": {"tokenizer": "my_tokenizer"}},"tokenizer": {"my_tokenizer": {"type": "path_hierarchy","delimiter": "-","replacement": "/","skip": 2}}}}
}
{"analyzer": "my_analyzer","text": "one-two-three-four-five"
}
解析结果:
[ /three, /three/four, /three/four/five ]
如果设置 reverse 为 true
[ one/two/three/, two/three/, three/ ]
uax_url_email 电子邮件分词器
{"tokenizer": "uax_url_email","text": "Email me at john.smith@global-international.com"
}
解析结果:
[ Email, me, at, john.smith@global-international.com ]
可配参数说明
- max_token_length
单个词语的最大长度。如果词语长度超过该长度,则按max_token_length间隔将其拆分。默认为255。
令牌过滤器
令牌过滤器,是在标记之后执行。es 提供的令牌过滤器非常多,我们只列一些可能会有用的来说一说。
uppercase 大写过滤器
{"tokenizer" : "standard","filter" : ["uppercase"],"text" : "the Quick FoX JUMPs"
}
解析结果
[ THE, QUICK, FOX, JUMPS ]
lowercase 小写过滤器
{"tokenizer" : "standard","filter" : ["lowercase"],"text" : "THE Quick FoX JUMPs"
}
解析结果:
[ the, quick, fox, jumps ]
stemmer 词干过滤器
{"tokenizer": "standard","filter": [ "stemmer" ],"text": "fox running and jumping jumped"
}
解析结果:
[ fox, run, and, jump, jump ]
注意标记提取了词干。比如:jumping 和 jumped 提取为了 jump 。
可配参数说明
- language
(可选,字符串)用于词干标记的依赖于语言的词干提取算法。可以设置很多语言,我们常用的也就 english(默认:英语)german 德语、spanish 西班牙语等等,但还是不包括中文。
stop 停用词过滤器
该过滤器默认将如下词语作为停用词:
a, an, and, are, as, at, be, but, by, for, if, in, into, is,
it, no, not, of, on, or, such, that, the, their, then, there,
these, they, this, to, was, will, with
{"tokenizer": "standard","filter": [ "stop" ],"text": "a quick fox jumps over the lazy dog"
}
解析结果:
[ quick, fox, jumps, over, lazy, dog ]
cjk_bigram 中日韩双字母标记过滤器
此过滤器支持中日韩的文字,但标记只对文字进行两两组合,严格上说对中文的支持也不是十分好。
{"tokenizer" : "standard","filter" : ["cjk_bigram"],"text" : "我们都是中国人"
}
解析结果:
{"tokens": [{"token": "我们","start_offset": 0,"end_offset": 2,"type": "<DOUBLE>","position": 0},{"token": "们都","start_offset": 1,"end_offset": 3,"type": "<DOUBLE>","position": 1},{"token": "都是","start_offset": 2,"end_offset": 4,"type": "<DOUBLE>","position": 2},{"token": "是中","start_offset": 3,"end_offset": 5,"type": "<DOUBLE>","position": 3},{"token": "中国","start_offset": 4,"end_offset": 6,"type": "<DOUBLE>","position": 4},{"token": "国人","start_offset": 5,"end_offset": 7,"type": "<DOUBLE>","position": 5}]
}
除去我们以上介绍的,ES 的令牌过滤器还有很多,我们就不过多说明了,因为他们大多数都是不支持中文的。