Token filter reference - Stop - 《Elasticsearch v7.9 Reference》

Stop token filter

Stop token filter

Removes stop words from a token stream.

When not customized, the filter removes the following English stop words by default:

a, an, and, are, as, at, be, but, by, for, if, in, into, is, it, no, not, of, on, or, such, that, the, their, then, there, these, they, this, to, was, will, with

In addition to English, the stop filter supports predefined stop word lists for several languages. You can also specify your own stop words as an array or file.

The stop filter uses Lucene’s StopFilter.

Example

The following analyze API request uses the stop filter to remove the stop words a and the from a quick fox jumps over the lazy dog:

GET /_analyze
{
  "tokenizer": "standard",
  "filter": [ "stop" ],
  "text": "a quick fox jumps over the lazy dog"
}

The filter produces the following tokens:

[ quick, fox, jumps, over, lazy, dog ]

Add to an analyzer

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

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

Configurable parameters

stopwords

(Optional, string or array of strings) Language value, such as _arabic_ or _thai_. Defaults to _english_.

Each language value corresponds to a predefined list of stop words in Lucene. See Stop words by language for supported language values and their stop words.

Also accepts an array of stop words.

For an empty list of stop words, use _none_.

stopwords_path

(Optional, string) Path to a file that contains a list of stop words to remove.

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

ignore_case

(Optional, boolean) If true, stop word matching is case insensitive. For example, if true, a stop word of the matches and removes The, THE, or the. Defaults to false.

remove_trailing

(Optional, boolean) If true, the last token of a stream is removed if it’s a stop word. Defaults to true.

This parameter should be false when using the filter with a completion suggester. This would ensure a query like green a matches and suggests green apple while still removing other stop words.

Customize

To customize the stop 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 case-insensitive stop filter that removes stop words from the _english_ stop words list:

PUT /my-index-000001
{
  "settings": {
    "analysis": {
      "analyzer": {
        "default": {
          "tokenizer": "whitespace",
          "filter": [ "my_custom_stop_words_filter" ]
        }
      },
      "filter": {
        "my_custom_stop_words_filter": {
          "type": "stop",
          "ignore_case": true
        }
      }
    }
  }
}

You can also specify your own list of stop words. For example, the following request creates a custom case-sensitive stop filter that removes only the stop words and, is, and the:

PUT /my-index-000001
{
  "settings": {
    "analysis": {
      "analyzer": {
        "default": {
          "tokenizer": "whitespace",
          "filter": [ "my_custom_stop_words_filter" ]
        }
      },
      "filter": {
        "my_custom_stop_words_filter": {
          "type": "stop",
          "ignore_case": true,
          "stopwords": [ "and", "is", "the" ]
        }
      }
    }
  }
}