[feat] add iceberg publish_changes and order by (#3172)

Author: xylaaaaa

docs/lakehouse/catalogs/iceberg-catalog.mdx

@@ -1794,6 +1794,25 @@ For an Iceberg Database, you must first drop all tables under the database befor
   );
   ```
 
+  Starting from version 4.1.0, Doris supports specifying sort columns when creating an Iceberg table. When writing data, the data will be sorted according to the specified sort columns to achieve better query performance.
+
+  ```sql
+  CREATE TABLE ordered_table (
+    `id` int NULL,
+    `name` text NULL,
+    `score` double NULL,
+    `create_time` datetimev2(6) NULL
+  )
+  ORDER BY  (`id` ASC NULLS FIRST, `score` DESC NULLS LAST)
+  PROPERTIES (
+    "write-format" = "parquet",
+    "write.parquet.compression-codec" = "zstd"
+  );
+  ```
+
+  - If no sort columns are specified, no sorting will be performed during writes.
+  - The default sort order is ASC NULLS FIRST.
+
   After creation, you can use the `SHOW CREATE TABLE` command to view the Iceberg table creation statement. For details about partition functions, see the [Partitioning](#) section.
 
 * **Dropping Tables**
@@ -2542,6 +2561,51 @@ EXECUTE set_current_snapshot ("ref" = "v1.0");
 3. The operation will fail if the specified snapshot ID or reference does not exist
 4. If the current snapshot is already the target snapshot, the operation returns directly without creating a new snapshot
 
+### publish_changes
+
+The `publish_changes` operation is used in the WAP (Write-Audit-Publish) mode to publish a snapshot with the specified `wap.id` as the current table state.  
+It locates the snapshot whose `wap.id` matches the given `wap_id` and cherry-picks it onto the current table, making the staged data visible to all read operations. 
+
+**Syntax:**
+
+```sql
+ALTER TABLE [catalog.][database.]table_name
+EXECUTE publish_changes("wap_id" = "<wap_id>")
+```
+
+**Parameters:**
+
+**Parameters:**
+
+| Parameter Name | Type | Required | Description |
+| -------------- | ---- | -------- | ----------- |
+| `wap_id` | STRING | Yes | The WAP snapshot ID to be published |
+
+**Return Value:**
+
+Executing `publish_changes` returns a result set with the following 2 columns:
+
+| Column Name | Type | Description |
+| ----------- | ---- | ----------- |
+| `previous_snapshot_id` | STRING | The ID of the current snapshot before the publish operation (NULL if none) |
+| `current_snapshot_id` | STRING | The ID of the new snapshot created and set as current after publishing |
+
+**Examples:**
+
+```sql
+-- Publish the snapshot whose WAP ID is test_wap_001
+ALTER TABLE iceberg_db.iceberg_table 
+EXECUTE publish_changes("wap_id" = "test_wap_001");
+```
+
+**Notes:**
+
+1. This operation does not support a WHERE clause, nor PARTITION/PARTITIONS clauses
+2. It is only meaningful for Iceberg tables with write.wap.enabled = true and WAP snapshots generated via wap.id
+3. If no snapshot is found for the specified wap_id, the operation fails and throws an error
+4. After publishing, the new snapshot becomes the current snapshot
+5. If there is no snapshot before publishing, previous_snapshot_id may be NULL
+
 ## Iceberg Table Optimization
 
 ### View Data File Distribution