Amazon web services 带“或”条件的Amazon DynamoDB

我刚从amazon dynamoDB开始，我必须创建一个类似这样的无sql数据库结构

-posts
    -postId1
        -tags
            1:A
            2:B
            3:C
        -text:Hello

    -postId2
        -tags
            1:B
            2:D
        -text:How are you?

    -postId3
        -tags   
            1:A
            2:C
        -text:Hello World

---

现在，我想检索那些带有标记B或D的帖子ID的文本，实现这一点最简单的方法是什么？

如评论中所述，如果您将标记属性维护为DynamoDB list数据类型，您可以使用CONTAINS with或operator来检查筛选带有标记B或D的帖子

扫描API的示例参数：-

完整代码：-

下面的代码使用本地DynamoDB

var AWS = require("aws-sdk");
var creds = new AWS.Credentials('akid', 'secret', 'session');

AWS.config.update({
    region: "us-west-2",
    endpoint: "http://localhost:8000",
    credentials: creds
});

var docClient = new AWS.DynamoDB.DocumentClient();

var params = {
    TableName: "post",
    FilterExpression: "contains (tags, :tag1) OR  contains (tags, :tag2)",
    ExpressionAttributeValues: {
        ":tag1": 'B',
        ":tag2": 'D'
    }
};

console.log("Scanning Post table.");
docClient.scan(params, onScan);

function onScan(err, data) {
    if (err) {
        console.error("Unable to scan the table. Error JSON:", JSON.stringify(err, null, 2));
    } else {
        console.log("Scan succeeded.");
        data.Items.forEach(function (printItem) {
            console.log("Item :", JSON.stringify(printItem));
        });

        if (typeof data.LastEvaluatedKey != "undefined") {
            console.log("Scanning for more...");
            params.ExclusiveStartKey = data.LastEvaluatedKey;
            docClient.scan(params, onScan);
        }
    }
}

---

看起来您需要执行操作。是否可以对标记列表中的多个项使用或条件？可以这样做，也可以只使用筛选器表达式中的关键字与枚举的值列表进行比较。我不确定你的标签是地图还是列表。它可以是任何东西，在这个结构中，我像地图一样显示它，但如果我使用列表，那就好了。类似的东西

var AWS = require("aws-sdk");
var creds = new AWS.Credentials('akid', 'secret', 'session');

AWS.config.update({
    region: "us-west-2",
    endpoint: "http://localhost:8000",
    credentials: creds
});

var docClient = new AWS.DynamoDB.DocumentClient();

var params = {
    TableName: "post",
    FilterExpression: "contains (tags, :tag1) OR  contains (tags, :tag2)",
    ExpressionAttributeValues: {
        ":tag1": 'B',
        ":tag2": 'D'
    }
};

console.log("Scanning Post table.");
docClient.scan(params, onScan);

function onScan(err, data) {
    if (err) {
        console.error("Unable to scan the table. Error JSON:", JSON.stringify(err, null, 2));
    } else {
        console.log("Scan succeeded.");
        data.Items.forEach(function (printItem) {
            console.log("Item :", JSON.stringify(printItem));
        });

        if (typeof data.LastEvaluatedKey != "undefined") {
            console.log("Scanning for more...");
            params.ExclusiveStartKey = data.LastEvaluatedKey;
            docClient.scan(params, onScan);
        }
    }
}