Question

我尝试从DynamoDB获取哪些userLimit介于较低和较高值之间。我使用JSON将较低的值发送给我的代码。我的Node.js代码：

var AWS = require('aws-sdk');
var db = new AWS.DynamoDB();


exports.handler = function(event, context) {

  var low=event.ke1;

  var params = {
    TableName: "Events", //"StreamsLambdaTable",
    ProjectionExpression: "userLimit, description",  //specifies the attributes you want in the scan result.
    FilterExpression: "userLimit between :lower and :higher",
    // ExpressionAttributeNames: {
    //     "#yr": "year",
    // },
    ExpressionAttributeValues: {
        ":lower": {"N": "low"},
        ":higher": {"N": "50"}
    }
};

  db.scan(params, function(err, data) {
    if (err) {
      console.log(err); // an error occurred
      } 
    else {
      data.Items.forEach(function(record) {
           console.log(
                record.description.S + "");
        });
        context.succeed(data.Items);
    // context.done(null,{"Result": "Operation succeeded."});
      //res.send(data.name);
      }
   // return next();
  });
};

我收到错误：

[ValidationException: ExpressionAttributeValues contains invalid value: The parameter cannot be converted to a numeric value: low for key :lower]
  message: 'ExpressionAttributeValues contains invalid value: The parameter cannot be converted to a numeric value: low for key :lower',

如果我将":lower": {"N": "low"},更改为":lower": {"N": low},，则错误为：

{ [ValidationException: ExpressionAttributeValues contains invalid value: Supplied AttributeValue is empty, must contain exactly one of the supported datatypes for key :lower]
  message: 'ExpressionAttributeValues contains invalid value: Supplied AttributeValue is empty, must contain exactly one of the supported datatypes for key :lower',

我的JSON数据是：

{
  "key1": "1"
}

如何使用key1的值设置较低的值？

编辑：

有错误：

 var low=event.ke1;

舒尔德

var low=event.key1;

编辑2：

运行该代码时发生了另一个错误：

 var params = {
    TableName: "Events", //"StreamsLambdaTable",
    ProjectionExpression: "userLimit, description, type",  //specifies the attributes you want in the scan result.
    KeyConditionExpression: "type = :tempType",
    // ExpressionAttributeNames: {
    //     "#yr": "year",
    // },
    ExpressionAttributeValues: {
        ":tempType": {"S": "Party"}
    }
};

错误：

{ [UnexpectedParameter: Unexpected key 'KeyConditionExpression' found in params]
  message: 'Unexpected key \'KeyConditionExpression\' found in params',

编辑3：

我目前的代码是：

var AWS = require('aws-sdk');
var db = new AWS.DynamoDB(); 


exports.handler = function(event, context) {

  var low=event.key1;

  var params = {
    TableName: "Events", //"StreamsLambdaTable",
    ProjectionExpression: "ID, userLimit, description, #tp",  //specifies the attributes you want in the scan result.
    KeyConditionExpression: "#tp = :tempType",
     ExpressionAttributeNames: {
         "#tp": "type",
     },
    ExpressionAttributeValues: {
        ":tempType": {"S": "Party"}
    }
};

  db.query(params, function(err, data) {
    if (err) {
      console.log(err); // an error occurred
      } 
    else {
      data.Items.forEach(function(record) {
           console.log(
                record.description.S + "");
        });
        context.succeed(data.Items);
    // context.done(null,{"Result": "Operation succeeded."});
      //res.send(data.name);
      }
   // return next();
  });
};

但是我收到了一个错误：

{ [ValidationException: Query condition missed key schema element: ID]
  message: 'Query condition missed key schema element: ID',

Answer 1

＆＃34; KeyConditionExpression＆＃34;不适用于scan操作。

如果属性是idexed字段，则需要更改要查询的操作;如果必须是扫描操作，则需要使用FilterExpression。

Answer 2

根据您的哈希键和索引，您可以使用：

DynamoDB查询：

var params = {
    TableName: 'table_name',
    KeyConditions: { // indexed attributes to query
                     // must include the hash key value of the table or index 
                     // with 'EQ' operator
        attribute_name: {
            ComparisonOperator: 'EQ', // (EQ | NE | IN | LE | LT | GE | GT | BETWEEN | 
                                      //  NOT_NULL | NULL | CONTAINS | NOT_CONTAINS | BEGINS_WITH)
            AttributeValueList: [ { S: 'STRING_VALUE' }, ],
        },
        // more key conditions ...
    }
};
dynamodb.query(params, function(err, data) {
    if (err) console.log(err); // an error occurred
    else console.log(data); // successful response
});

或DynamoDB扫描：

var params = {
    TableName: 'table_name',
    Limit: 0, // optional (limit the number of items to evaluate)
    ScanFilter: { // optional (map of attribute name to Condition)

        attribute_name: {
            ComparisonOperator: 'EQ', // (EQ | NE | IN | LE | LT | GE | GT | BETWEEN | 
                                      //  NOT_NULL | NULL | CONTAINS | NOT_CONTAINS | BEGINS_WITH)
            AttributeValueList: [ { S: 'STRING_VALUE' }, ],
        },
        // more conditions ...
    }
};
dynamodb.scan(params, function(err, data) {
    if (err) console.log(err); // an error occurred
    else console.log(data); // successful response
});

Node.js与DynamoDB-JSON的通信

2 个答案: