使用 DynamoDB.DocumentClient 成功进行 transactWrite 后，ItemCollectionMetrics 为空

Question

我正在对 DynamoDb 执行 transactWrite (https://docs.aws.amazon.com/AWSJavaScriptSDK/latest/AWS/DynamoDB/DocumentClient.html#transactWrite-property) 指令并期望返回 ItemCollectionMetrics（我在请求中指定 ReturnItemCollectionMetrics: 'SIZE'）。

对象返回为空 {}，即使在 dynamo 数据库表上发生了更改。

有人对此有想法吗？

代码

const dynamoResponse = await dynamoDbDocumentClient.transactWrite({
        TransactItems: [
            {
                Put: {
                    TableName: ENV.BLAH_CONTENT_COUNT_MESSAGES_TABLE,
                    ExpressionAttributeNames : {
                        '#v' : 'v',
                    },
                    ExpressionAttributeValues : {
                        ':v' : blah.v
                    },
                    ConditionExpression: '(attribute_exists(blahId) AND #v<>:v) OR attribute_not_exists(blahId)',
                    Item: {...blahCountMessage}
                }
            },
            {
                Update: {
                    TableName: ENV.BLAH_CONTENT_COUNTS_TABLE,
                    Key: { id: blahContentCount.id },
                    ExpressionAttributeNames : {
                        '#v' : 'v',
                        '#count' : 'count',
                        '#contentId': 'contentId'
                    },
                    ExpressionAttributeValues : {
                        ':v' : 1,
                        ':count' : deleted ? -1: 1,
                        ':contentId': blahContentCount.contentId,
                        ':defaultNumber': 0
                    },
                    ConditionExpression: 'attribute_not_exists(cognitoId)',
                    UpdateExpression: 'SET #contentId = :contentId, #count = if_not_exists(#count, :defaultNumber) + :count, #v = if_not_exists(#v, :defaultNumber) + :v',
                    ReturnValuesOnConditionCheckFailure: 'ALL_OLD'
                }
            }
        ],
        ReturnItemCollectionMetrics: 'SIZE'
    }).promise();

输出

console.log(JSON.stringify(dynamoResponse.ItemCollectionMetrics)); // {}

谢谢！

Answer 1

ReturnItemCollectionMetrics:

"Information about item collections, if any, that were affected by the operation. ItemCollectionMetrics is only returned if the request asked for it. If the table does not have any local secondary indexes, this information is not returned in the response."

根据：https://docs.aws.amazon.com/amazondynamodb/latest/APIReference/API_ItemCollectionMetrics.html

可能是此事务没有更新任何内容 - 或者您没有 LSI？

另请注意：文档说交易被禁用 "global tables"，我不太确定它们是不是指 GSI...但我不是使用 LSI 这可能也是为什么没有 ItemCollectionMetrics 的原因返回响应我的交易。

如果更新参数对象以包含 ReturnConsumedCapacity: 'TOTAL'，则响应对象应如下所示：

   [ { TableName: 'table_name',
       CapacityUnits: 8,
       WriteCapacityUnits: 8 } ] }

使用 DynamoDB.DocumentClient 成功进行 transactWrite 后，ItemCollectionMetrics 为空

ItemCollectionMetrics is empty after successful transactWrite using DynamoDB.DocumentClient

javascript

amazon-web-services

amazon-dynamodb

documentclient