Add mapping parameters to completion fields (#10295) (#10304)

Author: opensearch-trigger-bot[bot]

_field-types/supported-field-types/completion.md

@@ -37,6 +37,37 @@ PUT chess_store
 ```
 {% include copy-curl.html %}
 
+## Mapping parameters
+
+The `completion` field type supports the following mapping parameters.
+
+| Parameter   | Description   |
+| :--- | :--- |
+| `analyzer` | Specifies the index-time analyzer for input text. Default is `simple`. See [Index analyzers]({{site.url}}{{site.baseurl}}/analyzers/index-analyzers/).  |
+| `search_analyzer` | Defines the analyzer used at search time. Default is the value of `analyzer`. See [Search analyzers]({{site.url}}{{site.baseurl}}/analyzers/search-analyzers/). |
+| `preserve_separators` | If `true` (default), preserves separators such as spaces or punctuation. If set to `false`, allows queries like `queensg` to match a suggestion like "Queen's Gambit".    |
+| `preserve_position_increments` | If `true` (default), maintains position increments for analyzed tokens. Setting this to `false` can match suggestions like "The Sicilian Defense" when typing `s` because it skips over stopwords like "The". Alternatively, you can index both "Sicilian Defense" and "The Sicilian Defense" as separate inputs without changing the analyzer. |
+| `max_input_length`             | Limits the length of each input string. Default is `50` UTF-16 code points. This applies only at index time to prevent large inputs from bloating the underlying data structure. Most prefix completions work well within this limit.  |
+
+### Example mapping
+
+```json
+PUT chess_store
+{
+  "mappings": {
+    "properties": {
+      "suggestions": {
+        "type": "completion",
+        "analyzer": "standard"
+      },
+      "product": {
+        "type": "keyword"
+      }
+    }
+  }
+}
+```
+
 Index suggestions into OpenSearch:
 
 ```json
@@ -313,14 +344,14 @@ GET chess_store/_search
 To use all default fuzziness options, specify `"fuzzy": {}` or `"fuzzy": true`.
 {: .tip}
 
-The following table lists the parameters accepted by the fuzzy completion suggester query. All of the parameters are optional.
+The following table lists the parameters accepted by the `fuzzy` completion suggester query. All of the parameters are optional.
 
 Parameter | Description 
 :--- | :--- 
 `fuzziness` | Fuzziness can be set as one of the following: <br> 1. An integer that specifies the maximum allowed [Damerau–Levenshtein distance](https://en.wikipedia.org/wiki/Damerau–Levenshtein_distance) for this edit. <br> 2. `AUTO`: Strings of 0–2 characters must match exactly, strings of 3–5 characters allow 1 edit, and strings longer than 5 characters allow 2 edits.<br> Default is `AUTO`.
 `min_length` | An integer that specifies the minimum length the input must be to start returning suggestions. If the search term is shorter than `min_length`, no suggestions are returned. Default is 3.
 `prefix_length` | An integer that specifies the minimum length the matched prefix must be to start returning suggestions. If the prefix of `prefix_length` is not matched, but the search term is still within the Damerau–Levenshtein distance, no suggestions are returned. Default is 1.
-`transpositions` | A Boolean value that specifies to count transpositions (interchanges of adjacent characters) as one edit instead of two. Example: The suggestion's `input` parameter is `abcde` and the `fuzziness` is 1. If `transpositions` is set to `true`, `abdce` will match, but if `transpositions` is set to `false`, `abdce` will not match.  Default is `true`.
+`transpositions` | A Boolean value that specifies to count transpositions (interchanges of adjacent characters) as one edit instead of two. Example: The suggestion's `input` parameter is `abcde` and the `fuzziness` is 1. If `transpositions` is set to `true`, `abdce` will match, but if `transpositions` is set to `false`, `abdce` will not match. Default is `true`.
 `unicode_aware` | A Boolean value that specifies whether to use Unicode code points when measuring the edit distance, transposition, and length. If `unicode_aware` is set to `true`, the measurement is slower. Default is `false`, in which case distances are measured in bytes.
 
 ## Regex queries