# Preview the data source when created

Before creating the knowledge base, preview the number of files and data tables that will be selected based on the Catalog selection range. This interface is read-only and does not create knowledge bases, data sources, or processing tasks.

```text
POST https://moi.matrixorigin.cn/newmoi/semantic-models/source-selections/preview
```

## Preparation before calling

The selection range only supports Catalog data: `database_tables` is used for data tables in a Database, and `volume_files` is used for files in a Volume. Prepare `$AI_STUDIO_API_KEY` and `$WORKSPACE_ID`.

When `all_selected: false`, the corresponding `selected_table_ids` or `selected_file_ids` must be passed; when `all_selected: true`, the corresponding exclusion ID can be passed.

## Request example

```bash
curl -X POST "https://moi.matrixorigin.cn/newmoi/semantic-models/source-selections/preview" \
  -H "X-API-Key: $AI_STUDIO_API_KEY" \
  -H "X-Workspace-ID: $WORKSPACE_ID" \
  -H 'Content-Type: application/json' \
  -d '{
    "source_selections": [
      {
        "kind": "database_tables",
        "database_id": 101,
        "all_selected": false,
        "selected_table_ids": [201]
      }
    ]
  }'
```

## Successful response

Returns `200` on success.

```json
{
  "code": "OK",
  "msg": "OK",
  "data": {
    "file_count": 0,
    "table_count": 1,
    "total_count": 1
  }
}
```

| Field | Type | Description |
| --- | --- | --- |
| `data.file_count` | integer | The number of files in the preview range. |
| `data.table_count` | integer | The number of data tables in the preview range. |
| `data.total_count` | integer | The total quantity after deduplication. |

## Common mistakes

| HTTP Status Codes | Error Codes | Common Causes | Recommended Actions |
| --- | --- | --- | --- |
| `400` | `ErrParamInvalid` | The selection range is empty, or `kind`, ID, and selection rules are invalid. | Press [Create knowledge base and add data source](create-knowledge-base-with-sources.md) to correct the selection range. |
| `401` | `ErrUnauthorized` | The API Key is invalid or has expired. | Check API Key. |
| `403` | `ErrForbidden` | Does not have create permission or read permission for the selected range. | Check workspace and catalog object authorization. |

## Follow-up operations

Once the quantities are as expected, create the knowledge base and add the data source](create-knowledge-base-with-sources.md) using the same `source_selections` call.