如何使用 node.js 从`AWS dynamodb` 获取/扫描所有项目 [英] How to fetch/scan all items from `AWS dynamodb` using node.js
问题描述
如何使用 node.js
从 AWS dynamodb
获取/扫描所有项目.我在这里发布我的代码.
How to fetch/scan all items from AWS dynamodb
using node.js
. I am posting my code here.
var docClient = new aws.DynamoDB.DocumentClient();
var params = {
TableName:"users",
KeyConditionExpression:"user_status=:status",
ExpressionAttributeValues: {
":status": "Y"
}
};
var queryExecute = function(callback) {
docClient.query(params,function(err,result) {
if(err) {
console.log(err)
callback(err);
} else {
console.log(result);
if(result.LastEvaluatedKey) {
params.ExclusiveStartKey = result.LastEvaluatedKey;
queryExecute(callback);
} else {
callback(err,items);
}
}
});
}
queryExecute(callback);
这给了我以下错误.
ValidationException: Query condition missed key schema element: `user_id`.
这里的主键是 user_id.我不想在我的查询条件中使用它,因为如果我在 KeyConditionExpression
中提到了主键,我需要设置一个值.可能是我错了.但是,请建议我从 dynamodb
获取所有项目的好方法,它具有 user_status = "Y"
Here primary key is user_id. I don't want to use it with my query condition, because I need to set a value if I mentioned primary key in KeyConditionExpression
. May be I am wrong. However please suggest me a good way to fetch all items from dynamodb
, which is having user_status = "Y"
推荐答案
如果您想从 DynamoDB 获取数据而不使用 Hash 键值,则需要使用 Scan API
.
If you would like to get the data from DynamoDB without using Hash key value, you need to use Scan API
.
注意: Scan API 读取表中的所有项目以获取结果.因此,这是 DynamoDB 中的一项代价高昂的操作.
Note: The Scan API reads all the items in the table to get the results. So, it is a costly operation in DynamoDB.
替代方法:使用 GSI
以上场景扫码:-
var docClient = new AWS.DynamoDB.DocumentClient();
var params = {
TableName: "users",
FilterExpression: "#user_status = :user_status_val",
ExpressionAttributeNames: {
"#user_status": "user_status",
},
ExpressionAttributeValues: { ":user_status_val": 'somestatus' }
};
docClient.scan(params, onScan);
var count = 0;
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(itemdata) {
console.log("Item :", ++count,JSON.stringify(itemdata));
});
// continue scanning if we have more items
if (typeof data.LastEvaluatedKey != "undefined") {
console.log("Scanning for more...");
params.ExclusiveStartKey = data.LastEvaluatedKey;
docClient.scan(params, onScan);
}
}
}
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