Add dictionary decompounder docs #7979 (#7994) (#8749)

_analyzers/token-filters/dictionary-decompounder.md

@@ -0,0 +1,101 @@
+---
+layout: default
+title: Dictionary decompounder
+parent: Token filters
+nav_order: 110
+---
+
+# Dictionary decompounder token filter
+
+The `dictionary_decompounder` token filter is used to split compound words into their constituent parts based on a predefined dictionary. This filter is particularly useful for languages like German, Dutch, or Finnish, in which compound words are common, so breaking them down can improve search relevance. The `dictionary_decompounder` token filter determines whether each token (word) can be split into smaller tokens based on a list of known words. If the token can be split into known words, the filter generates the subtokens for the token.
+
+## Parameters
+
+The `dictionary_decompounder` token filter has the following parameters.
+
+Parameter | Required/Optional | Data type | Description
+:--- | :--- | :--- | :--- 
+`word_list` | Required unless `word_list_path` is configured | Array of strings | The dictionary of words that the filter uses to split compound words.
+`word_list_path` | Required unless `word_list` is configured | String | A file path to a text file containing the dictionary words. Accepts either an absolute path or a path relative to the `config` directory. The dictionary file must be UTF-8 encoded, and each word must be listed on a separate line.
+`min_word_size` | Optional | Integer | The minimum length of the entire compound word that will be considered for splitting. If a compound word is shorter than this value, it is not split. Default is `5`.
+`min_subword_size` | Optional | Integer | The minimum length for any subword. If a subword is shorter than this value, it is not included in the output. Default is `2`.
+`max_subword_size` | Optional | Integer | The maximum length for any subword. If a subword is longer than this value, it is not included in the output. Default is `15`.
+`only_longest_match` | Optional | Boolean | If set to `true`, only the longest matching subword will be returned. Default is `false`.
+
+## Example
+
+The following example request creates a new index named `decompound_example` and configures an analyzer with the `dictionary_decompounder` filter:
+
+```json
+PUT /decompound_example
+{
+  "settings": {
+    "analysis": {
+      "filter": {
+        "my_dictionary_decompounder": {
+          "type": "dictionary_decompounder",
+          "word_list": ["slow", "green", "turtle"]
+        }
+      },
+      "analyzer": {
+        "my_analyzer": {
+          "type": "custom",
+          "tokenizer": "standard",
+          "filter": ["lowercase", "my_dictionary_decompounder"]
+        }
+      }
+    }
+  }
+}
+```
+{% include copy-curl.html %}
+
+## Generated tokens
+
+Use the following request to examine the tokens generated using the analyzer:
+
+```json
+POST /decompound_example/_analyze
+{
+  "analyzer": "my_analyzer",
+  "text": "slowgreenturtleswim"
+}
+```
+{% include copy-curl.html %}
+
+The response contains the generated tokens:
+
+```json
+{
+  "tokens": [
+    {
+      "token": "slowgreenturtleswim",
+      "start_offset": 0,
+      "end_offset": 19,
+      "type": "<ALPHANUM>",
+      "position": 0
+    },
+    {
+      "token": "slow",
+      "start_offset": 0,
+      "end_offset": 19,
+      "type": "<ALPHANUM>",
+      "position": 0
+    },
+    {
+      "token": "green",
+      "start_offset": 0,
+      "end_offset": 19,
+      "type": "<ALPHANUM>",
+      "position": 0
+    },
+    {
+      "token": "turtle",
+      "start_offset": 0,
+      "end_offset": 19,
+      "type": "<ALPHANUM>",
+      "position": 0
+    }
+  ]
+}
+```

_analyzers/token-filters/index.md

@@ -25,7 +25,7 @@ Token filter | Underlying Lucene token filter|  Description
 [`decimal_digit`]({{site.url}}{{site.baseurl}}/analyzers/token-filters/decimal-digit/) | [DecimalDigitFilter](https://lucene.apache.org/core/9_10_0/analysis/common/org/apache/lucene/analysis/core/DecimalDigitFilter.html) | Converts all digits in the Unicode decimal number general category to basic Latin digits (0--9). 
 [`delimited_payload`]({{site.url}}{{site.baseurl}}/analyzers/token-filters/delimited-payload/) | [DelimitedPayloadTokenFilter](https://lucene.apache.org/core/9_10_0/analysis/common/org/apache/lucene/analysis/payloads/DelimitedPayloadTokenFilter.html) | Separates a token stream into tokens with corresponding payloads, based on a provided delimiter. A token consists of all characters preceding the delimiter, and a payload consists of all characters following the delimiter. For example, if the delimiter is `|`, then for the string `foo|bar`, `foo` is the token and `bar` is the payload. 
 [`delimited_term_freq`]({{site.url}}{{site.baseurl}}/analyzers/token-filters/delimited-term-frequency/) | [DelimitedTermFrequencyTokenFilter](https://lucene.apache.org/core/9_7_0/analysis/common/org/apache/lucene/analysis/miscellaneous/DelimitedTermFrequencyTokenFilter.html) | Separates a token stream into tokens with corresponding term frequencies, based on a provided delimiter. A token consists of all characters before the delimiter, and a term frequency is the integer after the delimiter. For example, if the delimiter is `|`, then for the string `foo|5`, `foo` is the token and `5` is the term frequency.
-`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.
+[`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) | Splits compound words into their constituent parts based on a predefined dictionary. Useful for many Germanic languages.
 `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.