Shingle token filter

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

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

  1. GET /_analyze
  2. {
  3.   "tokenizer": "whitespace",
  4.   "filter": [ "shingle" ],
  5.   "text": "quick brown fox jumps"
  6. }

The filter produces the following tokens:

  1. [ 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
  1. GET /_analyze
  2. {
  3.   "tokenizer": "whitespace",
  4.   "filter": [
  5.     {
  6.       "type": "shingle",
  7.       "min_shingle_size": 2,
  8.       "max_shingle_size": 3
  9.     }
  10.   ],
  11.   "text": "quick brown fox jumps"
  12. }

The filter produces the following tokens:

  1. [ 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.

  1. GET /_analyze
  2. {
  3.   "tokenizer": "whitespace",
  4.   "filter": [
  5.     {
  6.       "type": "shingle",
  7.       "min_shingle_size": 2,
  8.       "max_shingle_size": 3,
  9.       "output_unigrams": false
  10.     }
  11.   ],
  12.   "text": "quick brown fox jumps"
  13. }

The filter produces the following tokens:

  1. [ quick brown, quick brown fox, brown fox, brown fox jumps, fox jumps ]

Add to an analyzer

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

  1. PUT /my-index-000001
  2. {
  3.   "settings": {
  4.     "analysis": {
  5.       "analyzer": {
  6.         "standard_shingle": {
  7.           "tokenizer": "standard",
  8.           "filter": [ "shingle" ]
  9.         }
  10.       }
  11.     }
  12.   }
  13. }

Configurable parameters

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.

  1. GET /_analyze
  2. {
  3.   "tokenizer": "whitespace",
  4.   "filter": [
  5.     {
  6.       "type": "stop",
  7.       "stopwords": [ "a" ]
  8.     },
  9.     {
  10.       "type": "shingle",
  11.       "filler_token": "+"
  12.     }
  13.   ],
  14.   "text": "fox jumps a lazy dog"
  15. }

The filter produces the following tokens:

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

Customize

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.

  1. PUT /my-index-000001
  2. {
  3.   "settings": {
  4.     "analysis": {
  5.       "analyzer": {
  6.         "en": {
  7.           "tokenizer": "standard",
  8.           "filter": [ "my_shingle_filter" ]
  9.         }
  10.       },
  11.       "filter": {
  12.         "my_shingle_filter": {
  13.           "type": "shingle",
  14.           "min_shingle_size": 2,
  15.           "max_shingle_size": 5,
  16.           "output_unigrams": false
  17.         }
  18.       }
  19.     }
  20.   }
  21. }