为什么在 nodejs sdk v3 中发出 QueryCommand 时会出现错误？

Question

我正在使用 aws node.js sdk v3。我想使用 dynamodbdocumentclient 对表进行简单查询。我只想测试查询是否适用于 aws 开发人员指南提供的简单音乐表。

const data = await this.dynamoDBDocumentClient.send(new QueryCommand({
      TableName: "Music",
      KeyConditionExpression: "#Artist = :artist",
      ExpressionAttributeName: {
        "#Artist": "artist"

      },
      ExpressionAttributeValues: {
        ":artist": "Acme Band"
      },
    });

但是当我调用它时，我得到：

TypeError: Cannot read property '0' of undefined

当我做一个简单的时候：

const data = await.this.dynamoDBDocumentClient.send(newScanCommand({TableName: "Music"});

我得到了正确的回应：

            {
                "AlbumTitle": {
                    "S": "Somewhat Famous"
                },
                "Awards": {
                    "N": "1"
                },
                "Artist": {
                    "S": "No One You Know"
                },
                "SongTitle": {
                    "S": "Call Me Today"
                }
            },
            {
                "AlbumTitle": {
                    "S": "Songs About Life"
                },
                "Awards": {
                    "N": "10"
                },
                "Artist": {
                    "S": "Acme Band"
                },
                "SongTitle": {
                    "S": "Happy Day"
                }
            },
            {
                "AlbumTitle": {
                    "S": "Songs About Sadness"
                },
                "Awards": {
                    "N": "8"
                },
                "Artist": {
                    "S": "Acme Band"
                },
                "SongTitle": {
                    "S": "Sad Day"
                }
            }
        ],
        "ScannedCount": 3
    }```

What am I doing wrong? I don't get why I am getting en error.

Answer 1

我刚遇到同样的问题，根据this guide，ExpressionAttributeValues 必须遵循 DynamoDB JSON 模式，因此，如果您的 artist 是字符串，则应该是：

...
ExpressionAttributeValues: {
    ":artist": {S: "Acme Band"}
},
...

添加这个，对我有用。