Add shingle token filter docs (#8398) (#8844)

opensearch-project · Dec 2, 2024 · dadabf3 · dadabf3
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diff --git a/_analyzers/token-filters/index.md b/_analyzers/token-filters/index.md
@@ -52,7 +52,7 @@ Token filter | Underlying Lucene token filter|  Description
 [`predicate_token_filter`]({{site.url}}{{site.baseurl}}/analyzers/token-filters/predicate-token-filter/) | N/A | Removes tokens that do not match the specified predicate script. Supports only inline Painless scripts.
 [`remove_duplicates`]({{site.url}}{{site.baseurl}}/analyzers/token-filters/remove-duplicates/) | [RemoveDuplicatesTokenFilter](https://lucene.apache.org/core/9_10_0/analysis/common/org/apache/lucene/analysis/miscellaneous/RemoveDuplicatesTokenFilter.html) | Removes duplicate tokens that are in the same position.
 [`reverse`]({{site.url}}{{site.baseurl}}/analyzers/token-filters/reverse/) | [ReverseStringFilter](https://lucene.apache.org/core/9_10_0/analysis/common/org/apache/lucene/analysis/reverse/ReverseStringFilter.html) | Reverses the string corresponding to each token in the token stream. For example, the token `dog` becomes `god`.
-`shingle` | [ShingleFilter](https://lucene.apache.org/core/9_10_0/analysis/common/org/apache/lucene/analysis/shingle/ShingleFilter.html) | Generates shingles of lengths between `min_shingle_size` and `max_shingle_size` for tokens in the token stream. Shingles are similar to n-grams but apply to words instead of letters. For example, two-word shingles added to the list of unigrams [`contribute`, `to`, `opensearch`] are [`contribute to`, `to opensearch`].
+[`shingle`]({{site.url}}{{site.baseurl}}/analyzers/token-filters/shingle/) | [ShingleFilter](https://lucene.apache.org/core/9_10_0/analysis/common/org/apache/lucene/analysis/shingle/ShingleFilter.html) | Generates shingles of lengths between `min_shingle_size` and `max_shingle_size` for tokens in the token stream. Shingles are similar to n-grams but are generated using words instead of letters. For example, two-word shingles added to the list of unigrams [`contribute`, `to`, `opensearch`] are [`contribute to`, `to opensearch`].
 `snowball` | N/A | Stems words using a [Snowball-generated stemmer](https://snowballstem.org/). You can use the `snowball` token filter with the following languages in the `language` field: `Arabic`, `Armenian`, `Basque`, `Catalan`, `Danish`, `Dutch`, `English`, `Estonian`, `Finnish`, `French`, `German`, `German2`, `Hungarian`, `Irish`, `Italian`, `Kp`, `Lithuanian`, `Lovins`, `Norwegian`, `Porter`, `Portuguese`, `Romanian`, `Russian`, `Spanish`, `Swedish`, `Turkish`.
 `stemmer` | N/A | Provides algorithmic stemming for the following languages in the `language` field: `arabic`, `armenian`, `basque`, `bengali`, `brazilian`, `bulgarian`, `catalan`, `czech`, `danish`, `dutch`, `dutch_kp`, `english`, `light_english`, `lovins`, `minimal_english`, `porter2`, `possessive_english`, `estonian`, `finnish`, `light_finnish`, `french`, `light_french`, `minimal_french`, `galician`, `minimal_galician`, `german`, `german2`, `light_german`, `minimal_german`, `greek`, `hindi`, `hungarian`, `light_hungarian`, `indonesian`, `irish`, `italian`, `light_italian`, `latvian`, `Lithuanian`, `norwegian`, `light_norwegian`, `minimal_norwegian`, `light_nynorsk`, `minimal_nynorsk`, `portuguese`, `light_portuguese`, `minimal_portuguese`, `portuguese_rslp`, `romanian`, `russian`, `light_russian`, `sorani`, `spanish`, `light_spanish`, `swedish`, `light_swedish`, `turkish`.
 `stemmer_override` | N/A | Overrides stemming algorithms by applying a custom mapping so that the provided terms are not stemmed.

diff --git a/_analyzers/token-filters/shingle.md b/_analyzers/token-filters/shingle.md
@@ -0,0 +1,120 @@
+---
+layout: default
+title: Shingle
+parent: Token filters
+nav_order: 370
+---
+
+# Shingle token filter
+
+The `shingle` token filter is used to generate word n-grams, or _shingles_, from input text. For example, for the string `slow green turtle`, the `shingle` filter creates the following one- and two-word shingles: `slow`, `slow green`, `green`, `green turtle`, and `turtle`.
+
+This token filter is often used in conjunction with other filters to enhance search accuracy by indexing phrases rather than individual tokens. For more information, see [Phrase suggester]({{site.url}}{{site.baseurl}}/search-plugins/searching-data/did-you-mean/#phrase-suggester).
+
+## Parameters
+
+The `shingle` token filter can be configured with the following parameters.
+
+Parameter | Required/Optional | Data type | Description
+:--- | :--- | :--- | :--- 
+`min_shingle_size` | Optional | Integer | The minimum number of tokens to concatenate. Default is `2`.
+`max_shingle_size` | Optional | Integer | The maximum number of tokens to concatenate. Default is `2`.
+`output_unigrams` | Optional | Boolean | Whether to include unigrams (individual tokens) as output. Default is `true`.
+`output_unigrams_if_no_shingles` | Optional | Boolean | Whether to output unigrams if no shingles are generated. Default is `false`.
+`token_separator` | Optional | String |  A separator used to concatenate tokens into a shingle. Default is a space (`" "`).
+`filler_token` | Optional | String | A token inserted into empty positions or gaps between tokens. Default is an underscore (`_`).
+
+If `output_unigrams` and `output_unigrams_if_no_shingles` are both set to `true`, `output_unigrams_if_no_shingles` is ignored.
+{: .note}
+
+## Example
+
+The following example request creates a new index named `my-shingle-index` and configures an analyzer with a `shingle` filter:
+
+```json
+PUT /my-shingle-index
+{
+  "settings": {
+    "analysis": {
+      "filter": {
+        "my_shingle_filter": {
+          "type": "shingle",
+          "min_shingle_size": 2,
+          "max_shingle_size": 2,
+          "output_unigrams": true
+        }
+      },
+      "analyzer": {
+        "my_shingle_analyzer": {
+          "type": "custom",
+          "tokenizer": "standard",
+          "filter": [
+            "lowercase",
+            "my_shingle_filter"
+          ]
+        }
+      }
+    }
+  }
+}
+```
+{% include copy-curl.html %}
+
+## Generated tokens
+
+Use the following request to examine the tokens generated using the analyzer:
+
+```json
+GET /my-shingle-index/_analyze
+{
+  "analyzer": "my_shingle_analyzer",
+  "text": "slow green turtle"
+}
+```
+{% include copy-curl.html %}
+
+The response contains the generated tokens:
+
+```json
+{
+  "tokens": [
+    {
+      "token": "slow",
+      "start_offset": 0,
+      "end_offset": 4,
+      "type": "<ALPHANUM>",
+      "position": 0
+    },
+    {
+      "token": "slow green",
+      "start_offset": 0,
+      "end_offset": 10,
+      "type": "shingle",
+      "position": 0,
+      "positionLength": 2
+    },
+    {
+      "token": "green",
+      "start_offset": 5,
+      "end_offset": 10,
+      "type": "<ALPHANUM>",
+      "position": 1
+    },
+    {
+      "token": "green turtle",
+      "start_offset": 5,
+      "end_offset": 17,
+      "type": "shingle",
+      "position": 1,
+      "positionLength": 2
+    },
+    {
+      "token": "turtle",
+      "start_offset": 11,
+      "end_offset": 17,
+      "type": "<ALPHANUM>",
+      "position": 2
+    }
+  ]
+}
+```