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CJK width token filter

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CJK width token filter

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Normalizes width differences in CJK (Chinese, Japanese, and Korean) characters as follows:

Folds full-width ASCII character variants into the equivalent basic Latin characters
Folds half-width Katakana character variants into the equivalent Kana characters

This filter is included in Elasticsearch’s built-in CJK language analyzer. It uses Lucene’s CJKWidthFilter.

This token filter can be viewed as a subset of NFKC/NFKD Unicode normalization. See the analysis-icu plugin for full normalization support.

Example

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GET /_analyze
{
  "tokenizer" : "standard",
  "filter" : ["cjk_width"],
  "text" : "ｼｰｻｲﾄﾞﾗｲﾅｰ"
}

The filter produces the following token:

シーサイドライナー

Add to an analyzer

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The following create index API request uses the CJK width token filter to configure a new custom analyzer.

PUT /cjk_width_example
{
  "settings": {
    "analysis": {
      "analyzer": {
        "standard_cjk_width": {
          "tokenizer": "standard",
          "filter": [ "cjk_width" ]
        }
      }
    }
  }
}

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