> ## Documentation Index
> Fetch the complete documentation index at: https://risingwavelabs-wyx-add-timestamp-dedicated-page.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# ALTER SOURCE

> The `ALTER SOURCE` command modifies the definition of a source.

## Syntax

```sql theme={null}
ALTER SOURCE current_source_name
    alter_option;
```

*`alter_option`* depends on the operation you want to perform on the source. For all supported clauses, see the sections below.

## Clause

### `ADD COLUMN`

```sql theme={null}
ALTER SOURCE source_name
    ADD COLUMN col_name data_type;
```

| Parameter or clause | Description                                                                                                                                                                  |
| :------------------ | :--------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| **ADD COLUMN**      | This clause adds a column to the specified source.                                                                                                                           |
| *col\_name*         | The name of the new column you want to add to the source.                                                                                                                    |
| *data\_type*        | The data type of the newly added column. With the struct data type, you can create a nested table. Elements in a nested table need to be enclosed with angle brackets (\<>). |

```sql theme={null}
-- Add a column named "v3" to a source named "src1"
ALTER SOURCE src1
    ADD COLUMN v3 int;
```

<Note>
  * To alter columns in a source created with a schema registry, see [REFRESH SCHEMA](/sql/commands/sql-alter-source#refresh-schema).
  * You cannot add a primary key column to a source or table in RisingWave. To modify the primary key of a source or table, you need to recreate the table.
  * You cannot remove a column from a source in RisingWave. If you intend to remove a column from a source, you'll need to drop the source and create the source again.
</Note>

### `REFRESH SCHEMA`

Fetch the latest schema from the schema registry and update the source schema.

```sql theme={null}
ALTER SOURCE source_name REFRESH SCHEMA;
```

<Note>
  Currently when refreshing the schema registry of a source, it is not allowed to drop columns or change types.
</Note>

For example, assume we have a source as follows:

```sql Create a source theme={null}
CREATE SOURCE src_user WITH (
    connector = 'kafka',
    topic = 'sr_pb_test',
    properties.bootstrap.server = 'message_queue:29092',
    scan.startup.mode = 'earliest'
)
FORMAT PLAIN ENCODE PROTOBUF(
    schema.registry = 'http://message_queue:8081',
    message = 'test.User'
);
```

Then we can refresh its schema with the following statement:

```sql Refresh schema theme={null}
ALTER SOURCE src_user REFRESH SCHEMA;
```

### `RENAME TO`

```sql theme={null}
ALTER SOURCE source_name
    RENAME TO new_source_name;
```

| Parameter or clause | Description                                 |
| :------------------ | :------------------------------------------ |
| **RENAME TO**       | This clause changes the name of the source. |
| *new\_source\_name* | The new name of the source.                 |

```sql theme={null}
-- Change the name of a source named "src" to "src1"
ALTER SOURCE src
   RENAME TO src1;
```

### `OWNER TO`

```sql theme={null}
ALTER SOURCE current_source_name
    OWNER TO new_user;
```

| Parameter or clause | Description                                     |
| :------------------ | :---------------------------------------------- |
| **OWNER TO**        | This clause changes the owner of the source.    |
| *new\_user*         | The new owner you want to assign to the source. |

```sql theme={null}
-- Change the owner of the source named "src" to user "user1"
ALTER SOURCE src OWNER TO user1;
```

### `SET SCHEMA`

```sql theme={null}
ALTER SOURCE current_source_name
    SET SCHEMA schema_name;
```

| Parameter or clause | Description                                               |
| :------------------ | :-------------------------------------------------------- |
| **SET SCHEMA**      | This clause moves the source to a different schema.       |
| *schema\_name*      | The name of the schema to which the source will be moved. |

```sql theme={null}
-- Move the source named "test_source" to the schema named "test_schema"
ALTER SOURCE test_source SET SCHEMA test_schema;
```

### `SET PARALLELISM`

<Note>
  Added in version 2.3.
</Note>

```sql theme={null}
ALTER SOURCE source_name
SET PARALLELISM { TO | = } parallelism_number;
```

| Parameter or clause | Description                                                                                                                                                                                                             |
| :------------------ | :---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| **SET PARALLELISM** | This clause controls the degree of [parallelism](/reference/key-concepts#parallelism) for the targeted [streaming job](/reference/key-concepts#streaming-queries).                                                      |
| source\_name        | Should be a [shared source](/sql/commands/sql-create-source#shared-source).                                                                                                                                             |
| parallelism\_number | Can be ADAPTIVE or a fixed number (e.g., 1, 2, 3). Setting it to ADAPTIVE expands the job's parallelism to all available units, while a fixed number locks it at that value. Setting it to 0 is equivalent to ADAPTIVE. |

```sql theme={null}
ALTER SOURCE s_kafka SET PARALLELISM = 2;
```

### `SET SOURCE_RATE_LIMIT`

```sql theme={null}
ALTER SOURCE source_name
    SET SOURCE_RATE_LIMIT { TO | = } { default | rate_limit_number };
```

Use this statement to modify the rate limit of a source. For the specific value of `SOURCE_RATE_LIMIT`, refer to [How to view runtime parameters](/operate/view-configure-runtime-parameters/#how-to-view-runtime-parameters).

<Note>
  For a newly created materialized view on a source with historical data e.g. Kafka source, it will backfill from
  the source. The backfilling process will not be affected by the `SOURCE_RATE_LIMIT`
  of the source.

  To modify the rate limit of the backfilling process, please refer to [SET BACKFILL\_RATE\_LIMIT](/sql/commands/sql-alter-materialized-view#set-backfill-rate-limit).
</Note>

```sql Example theme={null}
-- Alter the rate limit of a source to default
ALTER SOURCE kafka_source SET source_rate_limit TO default;
```

```sql Example theme={null}
-- Alter the rate limit of a source to 1000
ALTER SOURCE kafka_source SET source_rate_limit TO 1000;
```

### `SWAP WITH`

```sql theme={null}
ALTER SOURCE name
SWAP WITH target_name;
```

| Parameter      | Description                                          |
| :------------- | :--------------------------------------------------- |
| *name*         | The current name of the source to swap.              |
| *target\_name* | The target name of the source you want to swap with. |

```sql theme={null}
-- Swap the names of the api_data source and the file_data source.
ALTER SOURCE api_data
SWAP WITH file_data;
```