Add fingerprint token filter #7982 (#8059) (#8751)

_analyzers/token-filters/fingerprint.md

@@ -0,0 +1,86 @@
+---
+layout: default
+title: Fingerprint
+parent: Token filters
+nav_order: 140
+---
+
+# Fingerprint token filter
+
+The `fingerprint` token filter is used to standardize and deduplicate text. This is particularly useful when consistency in text processing is crucial. The `fingerprint` token filter achieves this by processing text using the following steps:
+
+1. **Lowercasing**: Converts all text to lowercase.
+2. **Splitting**: Breaks the text into tokens.
+3. **Sorting**: Arranges the tokens in alphabetical order.
+4. **Removing duplicates**: Eliminates repeated tokens.
+5. **Joining tokens**: Combines the tokens into a single string, typically joined by a space or another specified separator.
+
+## Parameters
+
+The `fingerprint` token filter can be configured with the following two parameters.
+
+Parameter | Required/Optional | Data type | Description
+:--- | :--- | :--- | :--- 
+`max_output_size` | Optional | Integer | Limits the length of the generated fingerprint string. If the concatenated string exceeds the `max_output_size`, the filter will not produce any output, resulting in an empty token. Default is `255`.
+`separator` | Optional | String | Defines the character(s) used to join the tokens into a single string after they have been sorted and deduplicated. Default is space (`" "`).
+
+## Example
+
+The following example request creates a new index named `my_index` and configures an analyzer with a `fingerprint` token filter:
+
+```json
+PUT /my_index
+{
+  "settings": {
+    "analysis": {
+      "filter": {
+        "my_fingerprint": {
+          "type": "fingerprint",
+          "max_output_size": 200,
+          "separator": "-"
+        }
+      },
+      "analyzer": {
+        "my_analyzer": {
+          "type": "custom",
+          "tokenizer": "standard",
+          "filter": [
+            "lowercase",
+            "my_fingerprint"
+          ]
+        }
+      }
+    }
+  }
+}
+```
+{% include copy-curl.html %}
+
+## Generated tokens
+
+Use the following request to examine the tokens generated using the analyzer:
+
+```json
+POST /my_index/_analyze
+{
+  "analyzer": "my_analyzer",
+  "text": "OpenSearch is a powerful search engine that scales easily"
+}
+```
+{% include copy-curl.html %}
+
+The response contains the generated tokens:
+
+```json
+{
+  "tokens": [
+    {
+      "token": "a-easily-engine-is-opensearch-powerful-scales-search-that",
+      "start_offset": 0,
+      "end_offset": 57,
+      "type": "fingerprint",
+      "position": 0
+    }
+  ]
+}
+```

_analyzers/token-filters/index.md

@@ -28,7 +28,7 @@ Token filter | Underlying Lucene token filter|  Description
 [`dictionary_decompounder`]({{site.url}}{{site.baseurl}}/analyzers/token-filters/dictionary-decompounder/) | [DictionaryCompoundWordTokenFilter](https://lucene.apache.org/core/9_10_0/analysis/common/org/apache/lucene/analysis/compound/DictionaryCompoundWordTokenFilter.html) | Decomposes compound words found in many Germanic languages.
 [`edge_ngram`]({{site.url}}{{site.baseurl}}/analyzers/token-filters/edge-ngram/) | [EdgeNGramTokenFilter](https://lucene.apache.org/core/9_10_0/analysis/common/org/apache/lucene/analysis/ngram/EdgeNGramTokenFilter.html) | Tokenizes the given token into edge n-grams (n-grams that start at the beginning of the token) of lengths between `min_gram` and `max_gram`. Optionally, keeps the original token.
 `elision` | [ElisionFilter](https://lucene.apache.org/core/9_10_0/analysis/common/org/apache/lucene/analysis/util/ElisionFilter.html) | Removes the specified [elisions](https://en.wikipedia.org/wiki/Elision) from the beginning of tokens. For example, changes `l'avion` (the plane) to `avion` (plane).
-`fingerprint` | [FingerprintFilter](https://lucene.apache.org/core/9_10_0/analysis/common/org/apache/lucene/analysis/miscellaneous/FingerprintFilter.html) | Sorts and deduplicates the token list and concatenates tokens into a single token.
+[`fingerprint`]({{site.url}}{{site.baseurl}}/analyzers/token-filters/fingerprint/) | [FingerprintFilter](https://lucene.apache.org/core/9_10_0/analysis/common/org/apache/lucene/analysis/miscellaneous/FingerprintFilter.html) | Sorts and deduplicates the token list and concatenates tokens into a single token.
 `flatten_graph` | [FlattenGraphFilter](https://lucene.apache.org/core/9_10_0/analysis/common/org/apache/lucene/analysis/core/FlattenGraphFilter.html) | Flattens a token graph produced by a graph token filter, such as `synonym_graph` or `word_delimiter_graph`, making the graph suitable for indexing.
 `hunspell` | [HunspellStemFilter](https://lucene.apache.org/core/9_10_0/analysis/common/org/apache/lucene/analysis/hunspell/HunspellStemFilter.html) | Uses [Hunspell](https://en.wikipedia.org/wiki/Hunspell) rules to stem tokens. Because Hunspell supports a word having multiple stems, this filter can emit multiple tokens for each consumed token. Requires you to configure one or more language-specific Hunspell dictionaries.
 `hyphenation_decompounder` | [HyphenationCompoundWordTokenFilter](https://lucene.apache.org/core/9_8_0/analysis/common/org/apache/lucene/analysis/compound/HyphenationCompoundWordTokenFilter.html) | Uses XML-based hyphenation patterns to find potential subwords in compound words and checks the subwords against the specified word list. The token output contains only the subwords found in the word list.