IMPORTANT: No additional bug fixes or documentation updates will be released for this version. For the latest information, see the current release documentation.

« Snowball token filter Stemmer override token filter »

› › ›

Stemmer token filter

edit

IMPORTANT: This documentation is no longer updated. Refer to Elastic's version policy and the latest documentation.

Stemmer token filter

edit

Provides algorithmic stemming for several languages, some with additional variants. For a list of supported languages, see the language parameter.

When not customized, the filter uses the porter stemming algorithm for English.

Example

edit

The following analyze API request uses the stemmer filter’s default porter stemming algorithm to stem the foxes jumping quickly to the fox jump quickli:

GET /_analyze
{
  "tokenizer": "standard",
  "filter": [ "stemmer" ],
  "text": "the foxes jumping quickly"
}

The filter produces the following tokens:

[ the, fox, jump, quickli ]

Add to an analyzer

edit

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

PUT /my-index-000001
{
  "settings": {
    "analysis": {
      "analyzer": {
        "my_analyzer": {
          "tokenizer": "whitespace",
          "filter": [ "stemmer" ]
        }
      }
    }
  }
}

Configurable parameters

edit

language

(Optional, string) Language-dependent stemming algorithm used to stem tokens. If both this and the name parameter are specified, the language parameter argument is used.

Valid values for language

Valid values are sorted by language. Defaults to english. Recommended algorithms are bolded.

Arabic: arabic
Armenian: armenian
Basque: basque
Bengali: bengali
Brazilian Portuguese: brazilian
Bulgarian: bulgarian
Catalan: catalan
Czech: czech
Danish: danish
Dutch: dutch, dutch_kp
English: english, light_english, lovins, minimal_english, porter2, possessive_english
Estonian: estonian
Finnish: finnish, light_finnish
French: light_french, french, minimal_french
Galician: galician, minimal_galician (Plural step only)
German: light_german, german, german2, minimal_german
Greek: greek
Hindi: hindi
Hungarian: hungarian, light_hungarian
Indonesian: indonesian
Irish: irish
Italian: light_italian, italian
Kurdish (Sorani): sorani
Latvian: latvian
Lithuanian: lithuanian
Norwegian (Bokmål): norwegian, light_norwegian, minimal_norwegian
Norwegian (Nynorsk): light_nynorsk, minimal_nynorsk
Portuguese: light_portuguese, minimal_portuguese, portuguese, portuguese_rslp
Romanian: romanian
Russian: russian, light_russian
Spanish: light_spanish, spanish
Swedish: swedish, light_swedish
Turkish: turkish

name

An alias for the language parameter. If both this and the language parameter are specified, the language parameter argument is used.

Customize

edit

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

For example, the following request creates a custom stemmer filter that stems words using the light_german algorithm:

PUT /my-index-000001
{
  "settings": {
    "analysis": {
      "analyzer": {
        "my_analyzer": {
          "tokenizer": "standard",
          "filter": [
            "lowercase",
            "my_stemmer"
          ]
        }
      },
      "filter": {
        "my_stemmer": {
          "type": "stemmer",
          "language": "light_german"
        }
      }
    }
  }
}

« Snowball token filter Stemmer override token filter »