Function writeWithTransactionUsingDml

spanner/dml.js:371–464

(instanceId, databaseId, projectId)

}

async function writeWithTransactionUsingDml(instanceId, databaseId, projectId) {
  // [START spanner_dml_getting_started_update]
  // This sample transfers 200,000 from the MarketingBudget field
  // of the second Album to the first Album, as long as the second
  // Album has enough money in its budget. Make sure to run the
  // addColumn and updateData samples first (in that order).

  // Imports the Google Cloud client library
  const {Spanner} = require('@google-cloud/spanner');

  /**
   * TODO(developer): Uncomment the following lines before running the sample.
   */
  // const projectId = 'my-project-id';
  // const instanceId = 'my-instance';
  // const databaseId = 'my-database';

  // Creates a client
  const spanner = new Spanner({
    projectId: projectId,
  });

  // Gets a reference to a Cloud Spanner instance and database
  const instance = spanner.instance(instanceId);
  const database = instance.database(databaseId);

  const transferAmount = 200000;

  try {
    await database.runTransactionAsync(async transaction => {
      let firstBudget, secondBudget;
      const queryOne = `SELECT MarketingBudget FROM Albums
        WHERE SingerId = 2 AND AlbumId = 2`;

      const queryTwo = `SELECT MarketingBudget FROM Albums
      WHERE SingerId = 1 AND AlbumId = 1`;

      // Reads the second album's budget
      const [resultsOne] = await transaction.run(queryOne);
      const rowsOne = resultsOne.map(row => row.toJSON());
      secondBudget = rowsOne[0].MarketingBudget;
      console.log(`The second album's marketing budget: ${secondBudget}`);

      // Makes sure the second album's budget is large enough
      if (secondBudget < transferAmount) {
        throw new Error(
          `The second album's budget (${secondBudget}) is less than the transfer amount (${transferAmount}).`
        );
      }

      // Reads the first album's budget
      const [resultsTwo] = await transaction.run(queryTwo);
      const rowsTwo = resultsTwo.map(row => row.toJSON());
      firstBudget = rowsTwo[0].MarketingBudget;
      console.log(`The first album's marketing budget: ${firstBudget}`);

      // Transfers the budgets between the albums
      console.log(firstBudget, secondBudget);