Node.js（AWS SDK v3）中的 DynamoDB TransactWriteItems

import {DynamoDBClient, TransactWriteItemsCommand} from '@aws-sdk/client-dynamodb';

const client = new DynamoDBClient({region: 'us-east-1'});

// Move one award between two songs — atomically. If the first song has no
// award to give, NEITHER update happens.
const command = new TransactWriteItemsCommand({
  TransactItems: [
    {
      Update: {
        TableName: 'Music',
        Key: {Artist: {S: 'Arturo Sandoval'}, SongTitle: {S: 'Cubano Chant'}},
        UpdateExpression: 'SET #upd0 = #upd0 - :one',
        ConditionExpression: '#upd0 >= :one',
        ExpressionAttributeNames: {'#upd0': 'Awards'},
        ExpressionAttributeValues: {':one': {N: '1'}}
      }
    },
    {
      Update: {
        TableName: 'Music',
        Key: {Artist: {S: 'Arturo Sandoval'}, SongTitle: {S: 'A Mis Abuelos'}},
        UpdateExpression: 'SET #upd0 = if_not_exists(#upd0, :zero) + :one',
        ExpressionAttributeNames: {'#upd0': 'Awards'},
        ExpressionAttributeValues: {':one': {N: '1'}, ':zero': {N: '0'}}
      }
    }
  ]
});

try {
  await client.send(command);
  console.log('Transaction committed');
} catch (err) {
  if (err.name === 'TransactionCanceledException') {
    // One reason per action, in TransactItems order. 'None' means that action
    // was fine — some OTHER action sank the transaction.
    const codes = (err.CancellationReasons ?? []).map((r) => r.Code);
    console.log('Transaction canceled:', codes); // e.g. ['ConditionalCheckFailed', 'None']
  } else {
    throw err;
  }
}