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Character group tokenizer

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Character group tokenizer

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The char_group tokenizer breaks text into terms whenever it encounters a character which is in a defined set. It is mostly useful for cases where a simple custom tokenization is desired, and the overhead of use of the pattern tokenizer is not acceptable.

Configuration

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The char_group tokenizer accepts one parameter:

tokenize_on_chars

A list containing a list of characters to tokenize the string on. Whenever a character from this list is encountered, a new token is started. This accepts either single characters like e.g. -, or character groups: whitespace, letter, digit, punctuation, symbol.

max_token_length

The maximum token length. If a token is seen that exceeds this length then it is split at max_token_length intervals. Defaults to 255.

Example output

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POST _analyze
{
  "tokenizer": {
    "type": "char_group",
    "tokenize_on_chars": [
      "whitespace",
      "-",
      "\n"
    ]
  },
  "text": "The QUICK brown-fox"
}

returns

{
  "tokens": [
    {
      "token": "The",
      "start_offset": 0,
      "end_offset": 3,
      "type": "word",
      "position": 0
    },
    {
      "token": "QUICK",
      "start_offset": 4,
      "end_offset": 9,
      "type": "word",
      "position": 1
    },
    {
      "token": "brown",
      "start_offset": 10,
      "end_offset": 15,
      "type": "word",
      "position": 2
    },
    {
      "token": "fox",
      "start_offset": 16,
      "end_offset": 19,
      "type": "word",
      "position": 3
    }
  ]
}
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