BIGQUERY csv文件加载带有默认值的附加列

从Google提供的示例中，我已经按照指南（下面的链接和代码）设法将CSV文件加载到BigQuery（BQ）表中。
现在，我想向BQ中添加几个文件，并想添加一个filename包含文件名的新列。

有没有一种方法可以使用默认数据添加列？

https://cloud.google.com/bigquery/docs/loading-data-cloud-storage-csv

// Import the Google Cloud client libraries
const {BigQuery} = require('@google-cloud/bigquery');
const {Storage} = require('@google-cloud/storage');

// Instantiate clients
const bigquery = new BigQuery();
const storage = new Storage();

/**
 * This sample loads the CSV file at
 * https://storage.googleapis.com/cloud-samples-data/bigquery/us-states/us-states.csv
 *
 * TODO(developer): Replace the following lines with the path to your file.
 */
const bucketName = 'cloud-samples-data';
const filename = 'bigquery/us-states/us-states.csv';

async function loadCSVFromGCS() {
  // Imports a GCS file into a table with manually defined schema.

  /**
   * TODO(developer): Uncomment the following lines before running the sample.
   */
  // const datasetId = 'my_dataset';
  // const tableId = 'my_table';

  // Configure the load job. For full list of options, see:
  // https://cloud.google.com/bigquery/docs/reference/rest/v2/Job#JobConfigurationLoad
  const metadata = {
    sourceFormat: 'CSV',
    skipLeadingRows: 1,
    schema: {
      fields: [
        {name: 'name', type: 'STRING'},
        {name: 'post_abbr', type: 'STRING'},
//      {name: 'filemame', type: 'STRING', value=filename} // I WANT TO ADD COLUMN WITH FILE NAME HERE
      ],
    },
    location: 'US',
  };

  // Load data from a Google Cloud Storage file into the table
  const [job] = await bigquery
    .dataset(datasetId)
    .table(tableId)
    .load(storage.bucket(bucketName).file(filename), metadata);

  // load() waits for the job to finish
  console.log(`Job ${job.id} completed.`);

  // Check the job's status for errors
  const errors = job.status.errors;
  if (errors && errors.length > 0) {
    throw errors;
  }
}