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Shingle token filter

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Shingle token filter

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Add shingles, or word n-grams, to a token stream by concatenating adjacent tokens. By default, the shingle token filter outputs two-word shingles and unigrams.

For example, many tokenizers convert the lazy dog to [ the, lazy, dog ]. You can use the shingle filter to add two-word shingles to this stream: [ the, the lazy, lazy, lazy dog, dog ].

Shingles are often used to help speed up phrase queries, such as match_phrase. Rather than creating shingles using the shingles filter, we recommend you use the index-phrases mapping parameter on the appropriate text field instead.

This filter uses Lucene’s ShingleFilter.

Example

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The following analyze API request uses the shingle filter to add two-word shingles to the token stream for quick brown fox jumps:

GET /_analyze
{
  "tokenizer": "whitespace",
  "filter": [ "shingle" ],
  "text": "quick brown fox jumps"
}

The filter produces the following tokens:

[ quick, quick brown, brown, brown fox, fox, fox jumps, jumps ]

To produce shingles of 2-3 words, add the following arguments to the analyze API request:

min_shingle_size: 2
max_shingle_size: 3

GET /_analyze
{
  "tokenizer": "whitespace",
  "filter": [
    {
      "type": "shingle",
      "min_shingle_size": 2,
      "max_shingle_size": 3
    }
  ],
  "text": "quick brown fox jumps"
}

The filter produces the following tokens:

[ quick, quick brown, quick brown fox, brown, brown fox, brown fox jumps, fox, fox jumps, jumps ]

To only include shingles in the output, add an output_unigrams argument of false to the request.

GET /_analyze
{
  "tokenizer": "whitespace",
  "filter": [
    {
      "type": "shingle",
      "min_shingle_size": 2,
      "max_shingle_size": 3,
      "output_unigrams": false
    }
  ],
  "text": "quick brown fox jumps"
}

The filter produces the following tokens:

[ quick brown, quick brown fox, brown fox, brown fox jumps, fox jumps ]

Add to an analyzer

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

PUT /my_index
{
  "settings": {
    "analysis": {
      "analyzer": {
        "standard_shingle": {
          "tokenizer": "standard",
          "filter": [ "shingle" ]
        }
      }
    }
  }
}

Configurable parameters

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max_shingle_size

(Optional, integer) Maximum number of tokens to concatenate when creating shingles. Defaults to 2.

This value cannot be lower than the min_shingle_size argument, which defaults to 2. The difference between this value and the min_shingle_size argument cannot exceed the index.max_shingle_diff index-level setting, which defaults to 3.

min_shingle_size

(Optional, integer) Minimum number of tokens to concatenate when creating shingles. Defaults to 2.

This value cannot exceed the max_shingle_size argument, which defaults to 2. The difference between the max_shingle_size argument and this value cannot exceed the index.max_shingle_diff index-level setting, which defaults to 3.

output_unigrams

(Optional, boolean) If true, the output includes the original input tokens. If false, the output only includes shingles; the original input tokens are removed. Defaults to true.

output_unigrams_if_no_shingles

If true, the output includes the original input tokens only if no shingles are produced; if shingles are produced, the output only includes shingles. Defaults to false.

If both this and the output_unigrams parameter are true, only the output_unigrams argument is used.

token_separator

(Optional, string) Separator used to concatenate adjacent tokens to form a shingle. Defaults to a space (" ").

filler_token

(Optional, string) String used in shingles as a replacement for empty positions that do not contain a token. This filler token is only used in shingles, not original unigrams. Defaults to an underscore (_).

Some token filters, such as the stop filter, create empty positions when removing stop words with a position increment greater than one.

Example

In the following analyze API request, the stop filter removes the stop word a from fox jumps a lazy dog, creating an empty position. The subsequent shingle filter replaces this empty position with a plus sign (+) in shingles.

GET /_analyze
{
  "tokenizer": "whitespace",
  "filter": [
    {
      "type": "stop",
      "stopwords": [ "a" ]
    },
    {
      "type": "shingle",
      "filler_token": "+"
    }
  ],
  "text": "fox jumps a lazy dog"
}

The filter produces the following tokens:

[ fox, fox jumps, jumps, jumps +, + lazy, lazy, lazy dog, dog ]

Customize

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To customize the shingle 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 create index API request uses a custom shingle filter, my_shingle_filter, to configure a new custom analyzer.

The my_shingle_filter filter uses a min_shingle_size of 2 and a max_shingle_size of 5, meaning it produces shingles of 2-5 words. The filter also includes a output_unigrams argument of false, meaning that only shingles are included in the output.

PUT /my_index
{
  "settings": {
    "analysis": {
      "analyzer": {
        "en": {
          "tokenizer": "standard",
          "filter": [ "my_shingle_filter" ]
        }
      },
      "filter": {
        "my_shingle_filter": {
          "type": "shingle",
          "min_shingle_size": 2,
          "max_shingle_size": 5,
          "output_unigrams": false
        }
      }
    }
  }
}

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