transaction.js

// Copyright 2016 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

'use strict';

function readOnlyTransaction(instanceId, databaseId, projectId) {
  // [START spanner_read_only_transaction]
  // 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);

  // Gets a transaction object that captures the database state
  // at a specific point in time
  database.getSnapshot(async (err, transaction) => {
    if (err) {
      console.error(err);
      return;
    }
    const queryOne = 'SELECT SingerId, AlbumId, AlbumTitle FROM Albums';

    try {
      // Read #1, using SQL
      const [qOneRows] = await transaction.run(queryOne);

      qOneRows.forEach(row => {
        const json = row.toJSON();
        console.log(
          `SingerId: ${json.SingerId}, AlbumId: ${json.AlbumId}, AlbumTitle: ${json.AlbumTitle}`
        );
      });

      const queryTwo = {
        columns: ['SingerId', 'AlbumId', 'AlbumTitle'],
      };

      // Read #2, using the `read` method. Even if changes occur
      // in-between the reads, the transaction ensures that both
      // return the same data.
      const [qTwoRows] = await transaction.read('Albums', queryTwo);

      qTwoRows.forEach(row => {
        const json = row.toJSON();
        console.log(
          `SingerId: ${json.SingerId}, AlbumId: ${json.AlbumId}, AlbumTitle: ${json.AlbumTitle}`
        );
      });

      console.log('Successfully executed read-only transaction.');
    } catch (err) {
      console.error('ERROR:', err);
    } finally {
      transaction.end();
      // Close the database when finished.
      await database.close();
    }
  });
  // [END spanner_read_only_transaction]
}

function readWriteTransaction(instanceId, databaseId, projectId) {
  // [START spanner_read_write_transaction]
  // 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;

  database.runTransaction(async (err, transaction) => {
    if (err) {
      console.error(err);
      return;
    }
    let firstBudget, secondBudget;
    const queryOne = {
      columns: ['MarketingBudget'],
      keys: [[2, 2]], // SingerId: 2, AlbumId: 2
    };

    const queryTwo = {
      columns: ['MarketingBudget'],
      keys: [[1, 1]], // SingerId: 1, AlbumId: 1
    };

    Promise.all([
      // Reads the second album's budget
      transaction.read('Albums', queryOne).then(results => {
        // Gets second album's budget
        const rows = results[0].map(row => row.toJSON());
        secondBudget = rows[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
      transaction.read('Albums', queryTwo).then(results => {
        // Gets first album's budget
        const rows = results[0].map(row => row.toJSON());
        firstBudget = rows[0].MarketingBudget;
        console.log(`The first album's marketing budget: ${firstBudget}`);
      }),
    ])
      .then(() => {
        console.log(firstBudget, secondBudget);
        // Transfers the budgets between the albums
        firstBudget += transferAmount;
        secondBudget -= transferAmount;

        console.log(firstBudget, secondBudget);

        // Updates the database
        // Note: Cloud Spanner interprets Node.js numbers as FLOAT64s, so they
        // must be converted (back) to strings before being inserted as INT64s.
        transaction.update('Albums', [
          {
            SingerId: '1',
            AlbumId: '1',
            MarketingBudget: firstBudget.toString(),
          },
          {
            SingerId: '2',
            AlbumId: '2',
            MarketingBudget: secondBudget.toString(),
          },
        ]);
      })
      .then(() => {
        // Commits the transaction and send the changes to the database
        return transaction.commit();
      })
      .then(() => {
        console.log(
          `Successfully executed read-write transaction to transfer ${transferAmount} from Album 2 to Album 1.`
        );
      })
      .catch(err => {
        console.error('ERROR:', err);
      })
      .then(() => {
        transaction.end();
        // Closes the database when finished
        return database.close();
      });
  });
  // [END spanner_read_write_transaction]
}

require('yargs')
  .demand(1)
  .command(
    'readOnly <instanceName> <databaseName> <projectId>',
    'Execute a read-only transaction on an example Cloud Spanner table.',
    {},
    opts =>
      readOnlyTransaction(opts.instanceName, opts.databaseName, opts.projectId)
  )
  .command(
    'readWrite <instanceName> <databaseName> <projectId>',
    'Execute a read-write transaction on an example Cloud Spanner table.',
    {},
    opts =>
      readWriteTransaction(opts.instanceName, opts.databaseName, opts.projectId)
  )
  .example('node $0 readOnly "my-instance" "my-database" "my-project-id"')
  .example('node $0 readWrite "my-instance" "my-database" "my-project-id"')
  .wrap(120)
  .recommendCommands()
  .epilogue('For more information, see https://cloud.google.com/spanner/docs')
  .strict()
  .help().argv;