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Elastic Docs ›Elasticsearch Plugins and Integrations [5.5] ›Analysis Plugins ›Japanese (kuromoji) Analysis Plugin

kuromoji_stemmer token filter

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kuromoji_stemmer token filter

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The kuromoji_stemmer token filter normalizes common katakana spelling variations ending in a long sound character by removing this character (U+30FC). Only full-width katakana characters are supported.

This token filter accepts the following setting:

minimum_length
Katakana words shorter than the minimum length are not stemmed (default is 4). 
PUT kuromoji_sample
{
  "settings": {
    "index": {
      "analysis": {
        "analyzer": {
          "my_analyzer": {
            "tokenizer": "kuromoji_tokenizer",
            "filter": [
              "my_katakana_stemmer"
            ]
          }
        },
        "filter": {
          "my_katakana_stemmer": {
            "type": "kuromoji_stemmer",
            "minimum_length": 4
          }
        }
      }
    }
  }
}

POST kuromoji_sample/_analyze
{
  "analyzer": "my_analyzer",
  "text": "コピー" 
}

POST kuromoji_sample/_analyze
{
  "analyzer": "my_analyzer",
  "text": "サーバー" 
}

Returns コピー.

Return サーバ.

ja_stop token filter

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The ja_stop token filter filters out Japanese stopwords (_japanese_), and any other custom stopwords specified by the user. This filter only supports the predefined _japanese_ stopwords list. If you want to use a different predefined list, then use the stop token filter instead.

PUT kuromoji_sample
{
  "settings": {
    "index": {
      "analysis": {
        "analyzer": {
          "analyzer_with_ja_stop": {
            "tokenizer": "kuromoji_tokenizer",
            "filter": [
              "ja_stop"
            ]
          }
        },
        "filter": {
          "ja_stop": {
            "type": "ja_stop",
            "stopwords": [
              "_japanese_",
              "ストップ"
            ]
          }
        }
      }
    }
  }
}

POST kuromoji_sample/_analyze
{
  "analyzer": "analyzer_with_ja_stop",
  "text": "ストップは消える"
}

The above request returns:

{
  "tokens" : [ {
    "token" : "消える",
    "start_offset" : 5,
    "end_offset" : 8,
    "type" : "word",
    "position" : 2
  } ]
}

kuromoji_number token filter

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The kuromoji_number token filter normalizes Japanese numbers (kansūji) to regular Arabic decimal numbers in half-width characters. For example:

PUT kuromoji_sample
{
  "settings": {
    "index": {
      "analysis": {
        "analyzer": {
          "my_analyzer": {
            "tokenizer": "kuromoji_tokenizer",
            "filter": [
              "kuromoji_number"
            ]
          }
        }
      }
    }
  }
}

POST kuromoji_sample/_analyze
{
  "analyzer": "my_analyzer",
  "text": "一〇〇〇"
}

Which results in:

{
  "tokens" : [ {
    "token" : "1000",
    "start_offset" : 0,
    "end_offset" : 4,
    "type" : "word",
    "position" : 0
  } ]
}
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