adding snowball token filter docs opensearch-project#8276

Signed-off-by: Anton Rubin <[email protected]>
AntonEliatra · Sep 30, 2024 · 6684369 · 6684369
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diff --git a/_analyzers/token-filters/index.md b/_analyzers/token-filters/index.md
@@ -51,7 +51,7 @@ Normalization | `arabic_normalization`: [ArabicNormalizer](https://lucene.apache
 `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` | [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`].
-`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`.
+[`snowball`]({{site.url}}{{site.baseurl}}/analyzers/token-filters/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.
 `stop` | [StopFilter](https://lucene.apache.org/core/8_7_0/core/org/apache/lucene/analysis/StopFilter.html) | Removes stop words from a token stream.

diff --git a/_analyzers/token-filters/snowball.md b/_analyzers/token-filters/snowball.md
@@ -0,0 +1,108 @@
+---
+layout: default
+title: Snowball
+parent: Token filters
+nav_order: 380
+---
+
+# Snowball token filter
+
+The `snowball` token filter is a stemming filter based on the Snowball algorithm. It comes with support for many languages and offers improvement over the Porter stemming algorithm when it comes to efficiency and accuracy.
+
+## Parameters
+
+The `snowball` token filter can be configured with `language` parameter which can accept the following values:
+
+- Arabic
+- Armenian
+- Basque
+- Catalan
+- Danish
+- Dutch
+- English (Default)
+- Estonian
+- Finnish
+- French
+- German
+- German2 
+- Hungarian
+- Italian
+- Irish
+- Kp
+- Lithuanian
+- Lovins
+- Norwegian
+- Porter
+- Portuguese
+- Romanian
+- Russian
+- Spanish
+- Swedish
+- Turkish
+
+## Example
+
+The following example request creates a new index named `my-snowball-index` and configures an analyzer with `snowball` filter:
+
+```json
+PUT /my-snowball-index
+{
+  "settings": {
+    "analysis": {
+      "filter": {
+        "my_snowball_filter": {
+          "type": "snowball",
+          "language": "English"
+        }
+      },
+      "analyzer": {
+        "my_snowball_analyzer": {
+          "type": "custom",
+          "tokenizer": "standard",
+          "filter": [
+            "lowercase",
+            "my_snowball_filter"
+          ]
+        }
+      }
+    }
+  }
+}
+```
+{% include copy-curl.html %}
+
+## Generated tokens
+
+Use the following request to examine the tokens generated using the analyzer:
+
+```json
+GET /my-snowball-index/_analyze
+{
+  "analyzer": "my_snowball_analyzer",
+  "text": "running runners"
+}
+```
+{% include copy-curl.html %}
+
+The response contains the generated tokens:
+
+```json
+{
+  "tokens": [
+    {
+      "token": "run",
+      "start_offset": 0,
+      "end_offset": 7,
+      "type": "<ALPHANUM>",
+      "position": 0
+    },
+    {
+      "token": "runner",
+      "start_offset": 8,
+      "end_offset": 15,
+      "type": "<ALPHANUM>",
+      "position": 1
+    }
+  ]
+}
+```