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Elasticsearch（简称 ES）提供了多种预置的分词器（Analyzer），用于对文本进行分词处理。分词器通常由字符过滤器（Character Filters）、分词器（Tokenizer）和词元过滤器（Token Filters）组成。以下是一些常用的预置分词器及其示例：

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1. Standard Analyzer（标准分词器）

• 默认分词器，适用于大多数语言。
• 处理步骤：
  1. 使用标准分词器（Standard Tokenizer）按空格和标点符号分词。
  2. 应用小写过滤器（Lowercase Token Filter）将词元转换为小写。
• 示例：

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

  输出：

  ["the", "2", "quick", "brown", "foxes", "jumped", "over", "the", "lazy", "dog's", "bone"]
  

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2. Simple Analyzer（简单分词器）

• 按非字母字符（如数字、标点符号）分词，并将词元转换为小写。
• 示例：

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

  输出：

  ["the", "quick", "brown", "foxes", "jumped", "over", "the", "lazy", "dog", "s", "bone"]
  

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3. Whitespace Analyzer（空格分词器）

• 仅按空格分词，不转换大小写，不处理标点符号。
• 示例：

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

  输出：

  ["The", "2", "QUICK", "Brown-Foxes", "jumped", "over", "the", "lazy", "dog's", "bone."]
  

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4. Keyword Analyzer（关键词分词器）

• 将整个文本作为一个单独的词元，不做任何分词处理。
• 示例：

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

  输出：

  ["The 2 QUICK Brown-Foxes jumped over the lazy dog's bone."]
  

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5. Stop Analyzer（停用词分词器）

• 类似于简单分词器，但会过滤掉常见的停用词（如 “the”, “and”, “a” 等）。
• 示例：

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

  输出：

  ["quick", "brown", "foxes", "jumped", "over", "lazy", "dog", "s", "bone"]
  

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6. Pattern Analyzer（正则分词器）

• 使用正则表达式定义分词规则。
• 示例：

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

  默认按非字母字符分词，并转换为小写：

  ["the", "2", "quick", "brown", "foxes", "jumped", "over", "the", "lazy", "dog", "s", "bone"]
  

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7. Language Analyzer（语言分词器）

• 针对特定语言优化，支持多种语言（如英语、中文、法语等）。
• 示例（英语）：

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

  输出：

  ["2", "quick", "brown", "fox", "jump", "over", "lazi", "dog", "bone"]
  

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8. ICU Analyzer（国际化分词器）

• 基于 ICU（International Components for Unicode）库，支持多语言分词。
• 示例：

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

  输出：

  ["the", "2", "quick", "brown", "foxes", "jumped", "over", "the", "lazy", "dog's", "bone"]
  

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9. Fingerprint Analyzer（指纹分词器）

• 对文本进行分词、去重、排序，并生成唯一的“指纹”。
• 示例：

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

  输出：

  ["2", "bone", "brown", "dog", "foxes", "jumped", "lazy", "over", "quick", "the"]
  

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总结

Elasticsearch 的预置分词器适用于不同的场景，开发者可以根据需求选择合适的分析器，或者自定义分词器以满足特定需求。