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Elastic Docs ›Elasticsearch Guide [8.10] ›Text analysis ›Character filters reference

Mapping character filter

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Mapping character filter

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The mapping character filter accepts a map of keys and values. Whenever it encounters a string of characters that is the same as a key, it replaces them with the value associated with that key.

Matching is greedy; the longest pattern matching at a given point wins. Replacements are allowed to be the empty string.

The mapping filter uses Lucene’s MappingCharFilter.

Example

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The following analyze API request uses the mapping filter to convert Hindu-Arabic numerals (٠‎١٢٣٤٥٦٧٨‎٩‎) into their Arabic-Latin equivalents (0123456789), changing the text My license plate is ٢٥٠١٥ to My license plate is 25015.

response = client.indices.analyze(
  body: {
    tokenizer: 'keyword',
    char_filter: [
      {
        type: 'mapping',
        mappings: [
          '٠ => 0',
          '١ => 1',
          '٢ => 2',
          '٣ => 3',
          '٤ => 4',
          '٥ => 5',
          '٦ => 6',
          '٧ => 7',
          '٨ => 8',
          '٩ => 9'
        ]
      }
    ],
    text: 'My license plate is ٢٥٠١٥'
  }
)
puts response
GET /_analyze
{
  "tokenizer": "keyword",
  "char_filter": [
    {
      "type": "mapping",
      "mappings": [
        "٠ => 0",
        "١ => 1",
        "٢ => 2",
        "٣ => 3",
        "٤ => 4",
        "٥ => 5",
        "٦ => 6",
        "٧ => 7",
        "٨ => 8",
        "٩ => 9"
      ]
    }
  ],
  "text": "My license plate is ٢٥٠١٥"
}

The filter produces the following text:

[ My license plate is 25015 ]

Configurable parameters

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mappings

(Required*, array of strings) Array of mappings, with each element having the form key => value.

Either this or the mappings_path parameter must be specified.

mappings_path

(Required*, string) Path to a file containing key => value mappings.

This path must be absolute or relative to the config location, and the file must be UTF-8 encoded. Each mapping in the file must be separated by a line break.

Either this or the mappings parameter must be specified.

Customize and add to an analyzer

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To customize the mappings filter, duplicate it to create the basis for a new custom character filter. You can modify the filter using its configurable parameters.

The following create index API request configures a new custom analyzer using a custom mappings filter, my_mappings_char_filter.

The my_mappings_char_filter filter replaces the :) and :( emoticons with a text equivalent.

response = client.indices.create(
  index: 'my-index-000001',
  body: {
    settings: {
      analysis: {
        analyzer: {
          my_analyzer: {
            tokenizer: 'standard',
            char_filter: [
              'my_mappings_char_filter'
            ]
          }
        },
        char_filter: {
          my_mappings_char_filter: {
            type: 'mapping',
            mappings: [
              ':) => _happy_',
              ':( => _sad_'
            ]
          }
        }
      }
    }
  }
)
puts response
PUT /my-index-000001
{
  "settings": {
    "analysis": {
      "analyzer": {
        "my_analyzer": {
          "tokenizer": "standard",
          "char_filter": [
            "my_mappings_char_filter"
          ]
        }
      },
      "char_filter": {
        "my_mappings_char_filter": {
          "type": "mapping",
          "mappings": [
            ":) => _happy_",
            ":( => _sad_"
          ]
        }
      }
    }
  }
}

The following analyze API request uses the custom my_mappings_char_filter to replace :( with _sad_ in the text I'm delighted about it :(.

GET /my-index-000001/_analyze
{
  "tokenizer": "keyword",
  "char_filter": [ "my_mappings_char_filter" ],
  "text": "I'm delighted about it :("
}

The filter produces the following text:

[ I'm delighted about it _sad_ ]
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