docs: add docs for 'REFRESH NGRAM INDEX' (#2451)

Author: KKould

docs/cn/guides/55-performance/ngram-index.md

@@ -164,11 +164,12 @@ TableScan
 
 完整命令参考详见 [Ngram 索引](/sql/sql-commands/ddl/ngram-index/)。
 
-| 命令 | 用途 |
-|---------|---------|
+| 命令                                                       | 用途                   |
+|----------------------------------------------------------|----------------------|
 | `CREATE NGRAM INDEX name ON table(column) gram_size = N` | 创建含 N 字符片段的 ngram 索引 |
-| `SHOW INDEXES` | 列出所有索引（含 ngram 索引） |
-| `DROP NGRAM INDEX name ON table` | 删除 ngram 索引 |
+| `SHOW INDEXES`                                           | 列出所有索引（含 ngram 索引）   |
+| `REFRESH NGRAM INDEX name ON table`                      | 刷新 ngram 索引          |
+| `DROP NGRAM INDEX name ON table`                         | 删除 ngram 索引          |
 
 :::tip **使用场景**
 **适用：**

docs/cn/sql-reference/10-sql-commands/00-ddl/07-ngram-index/index.md

@@ -9,10 +9,11 @@ import EEFeature from '@site/src/components/EEFeature';
 
 ## Ngram 索引管理
 
-| 命令 | 描述 |
-|---------|-------------|
-| [CREATE NGRAM INDEX](create-ngram-index.md) | 创建新的 Ngram 索引用于高效子字符串搜索 |
-| [DROP NGRAM INDEX](drop-ngram-index.md) | 删除 Ngram 索引 |
+| 命令                                            | 描述                      |
+|-----------------------------------------------|-------------------------|
+| [CREATE NGRAM INDEX](create-ngram-index.md)   | 创建新的 Ngram 索引用于高效子字符串搜索 |
+| [REFRESH NGRAM INDEX](refresh-ngram-index.md) | 刷新 Ngram 索引             |
+| [DROP NGRAM INDEX](drop-ngram-index.md)       | 删除 Ngram 索引             |
 
 :::note
 Databend 的 Ngram 索引支持在文本数据中高效执行子字符串及模式匹配搜索，可显著提升 LIKE 等操作的性能。

docs/cn/sql-reference/10-sql-commands/00-ddl/07-ngram-index/refresh-ngram-index.md

@@ -0,0 +1,29 @@
+---
+title: REFRESH NGRAM INDEX
+sidebar_position: 2
+---
+
+import FunctionDescription from '@site/src/components/FunctionDescription';
+
+<FunctionDescription description="Introduced or updated: v1.2.726"/>
+
+import EEFeature from '@site/src/components/EEFeature';
+
+<EEFeature featureName='NGRAM INDEX'/>
+
+从表中刷新现有的 NGRAM 索引。
+
+## 语法
+
+```sql
+REFRESH NGRAM INDEX [IF EXISTS] <index_name>
+ON [<database>.]<table_name>;
+```
+
+## 示例
+
+以下示例从 `amazon_reviews_ngram` 表中刷新 `idx1` 索引：
+
+```sql
+REFRESH NGRAM INDEX idx1 ON amazon_reviews_ngram;
+```

docs/en/guides/55-performance/ngram-index.md

@@ -165,11 +165,12 @@ TableScan
 
 For complete command reference, see [Ngram Index](/sql/sql-commands/ddl/ngram-index/).
 
-| Command | Purpose |
-|---------|---------|
+| Command                                                  | Purpose                                      |
+|----------------------------------------------------------|----------------------------------------------|
 | `CREATE NGRAM INDEX name ON table(column) gram_size = N` | Create ngram index with N-character segments |
-| `SHOW INDEXES` | List all indexes including ngram indexes |
-| `DROP NGRAM INDEX name ON table` | Remove ngram index |
+| `SHOW INDEXES`                                           | List all indexes including ngram indexes     |
+| `REFRESH NGRAM INDEX name ON table`                      | Refresh ngram index                          |
+| `DROP NGRAM INDEX name ON table`                         | Remove ngram index                           |
 
 :::tip **When to Use Ngram Indexes**
 **Ideal for:**

docs/en/sql-reference/10-sql-commands/00-ddl/07-ngram-index/index.md

@@ -9,10 +9,11 @@ This page provides a comprehensive overview of Ngram index operations in Databen
 
 ## Ngram Index Management
 
-| Command | Description |
-|---------|-------------|
-| [CREATE NGRAM INDEX](create-ngram-index.md) | Creates a new Ngram index for efficient substring search |
-| [DROP NGRAM INDEX](drop-ngram-index.md) | Removes an Ngram index |
+| Command                                       | Description                                              |
+|-----------------------------------------------|----------------------------------------------------------|
+| [CREATE NGRAM INDEX](create-ngram-index.md)   | Creates a new Ngram index for efficient substring search |
+| [REFRESH NGRAM INDEX](refresh-ngram-index.md) | Refreshes an Ngram index                                 |
+| [DROP NGRAM INDEX](drop-ngram-index.md)       | Removes an Ngram index                                   |
 
 :::note
 Ngram indexes in Databend enable efficient substring and pattern matching searches within text data, improving performance for LIKE and similar operations.

docs/en/sql-reference/10-sql-commands/00-ddl/07-ngram-index/refresh-ngram-index.md

@@ -0,0 +1,29 @@
+---
+title: REFRESH NGRAM INDEX
+sidebar_position: 2
+---
+
+import FunctionDescription from '@site/src/components/FunctionDescription';
+
+<FunctionDescription description="Introduced or updated: v1.2.726"/>
+
+import EEFeature from '@site/src/components/EEFeature';
+
+<EEFeature featureName='NGRAM INDEX'/>
+
+Refresh an existing NGRAM index from a table.
+
+## Syntax
+
+```sql
+REFRESH NGRAM INDEX [IF EXISTS] <index_name>
+ON [<database>.]<table_name>;
+```
+
+## Examples
+
+The following example refreshes the `idx1` index from the `amazon_reviews_ngram` table:
+
+```sql
+REFRESH NGRAM INDEX idx1 ON amazon_reviews_ngram;
+```