aws - 如何设置 lambda 函数以对 dynamodb 进行动态查询

Question

这是我当前的 lambda 函数，它返回表“横幅”中的所有数据。

getBanner.js

'use strict'
const AWS = require('aws-sdk');

exports.handler = async function (event, context, callback) {
    const documentClient = new AWS.DynamoDB.DocumentClient();

    let responseBody = "";
    let statusCode = 0;

    const params = {
        TableName : "Banner",
    };

    try{
        const data = await documentClient.scan(params).promise();
        responseBody = JSON.stringify(data.Items);
        statusCode = 200
    }catch(err){
        responseBody = `Unable to get products: ${err}`;
        statusCode = 403
    }

    const response = {
        statusCode: statusCode,
        headers:{
            "Content-Type": "application/json",
            'Access-Control-Allow-Origin': '*', // Required for CORS support to work
        },
        body: responseBody
    }

    return response
}

是样本返回数据

[
   {
       Order: 123,
       Year: 2000
       ...
   },
   {
       Order: 77,
       Year: 2007
       ...
   }
]

我明白了如果我想查询属性顺序，我需要改为following。

...
var params = {
    TableName : "Banner",
    KeyConditionExpression: "#od = :yyyy",
    ExpressionAttributeNames:{
        "#od": "order"
    },
    ExpressionAttributeValues: {
        ":yyyy": 1
    }
};
...

如果我想执行以下操作怎么办？
可能有一些用例让我需要查询另一个属性或多个属性。

我应该如何拥有一个可以动态处理 queryStringParameters 的函数？

根据评论更新，但又出现错误

'use strict'
const AWS = require('aws-sdk');

exports.handler = async function (event, context, callback) {
    const documentClient = new AWS.DynamoDB.DocumentClient();

    let responseBody = "";
    let statusCode = 0;

    console.log(event)
    const queryStringParams = event.queryStringParameters;

    console.log(queryStringParams)

    let KeyConditionExpression = ''
    let ExpressionAttributeNames={};
    let ExpressionAttributeValues = {};
    for (const property in queryStringParams) {
      KeyConditionExpression += ` #${property} = :${property} ,`;
      ExpressionAttributeNames['#'+property] = property ;
      ExpressionAttributeValues[':'+property]=queryStringParams[property];
    }

    KeyConditionExpression= KeyConditionExpression.slice(0, -1);

    const params = {
        TableName : "Banner",
        KeyConditionExpression: KeyConditionExpression,
        ExpressionAttributeNames: ExpressionAttributeNames,
        ExpressionAttributeValues: ExpressionAttributeValues
    };

    console.log(params)   //Response A

    try{
        const data = await documentClient.scan(params).promise();
        responseBody = JSON.stringify(data.Items);
        statusCode = 200
    }catch(err){
        responseBody = `Unabel to get products: ${err}`;
        statusCode = 403
    }

    const response = {
        statusCode: statusCode,
        headers:{
            "Content-Type": "application/json",
            'Access-Control-Allow-Origin': '*', // Required for CORS support to work
        },
        body: responseBody
    }

    return response
}

Unabel to get products: ValidationException: ExpressionAttributeNames can only be specified when using expressions

这是从 cloudwatch 获得的‘params’的值 回应A

{
  TableName: 'Banner',
  KeyConditionExpression: ' #order = :order , #year = :year ',
  ExpressionAttributeNames: { '#order': 'order', '#year': 'year' },
  ExpressionAttributeValues: { ':order': '1', ':year': '2007' }
}

Answer 1

简单示例

const getParams = (key, value) => ({
  TableName: "Banner",
  KeyConditionExpression: "#key = :value",
  ExpressionAttributeNames: {
    "#key": key
  },
  ExpressionAttributeValues: {
    ":value": value
  }
});

并根据您的查询参数调用此函数。 可以从事件中获取的查询参数。

const queryParams = event.queryStringParameters;

Answer 2

您可以从您的 Lambda 函数处理程序中的事件对象中查询参数。事件对象内容取决于调用 Lambda 函数的服务。如果从 Elastic Load Balancing 或 API 网关调用 Lambda 函数，您可以从事件对象中获取查询参数。事件对象将有一个名为queryStringParameters 的属性，其中包含请求中的所有查询字符串参数。

这是文档中事件对象的示例：

{
    "requestContext": {
        "elb": {
            "targetGroupArn": "arn:aws:elasticloadbalancing:us-east-2:123456789012:targetgroup/lambda-279XGJDqGZ5rsrHC2Fjr/49e9d65c45c6791a"
        }
    },
    "httpMethod": "GET",
    "path": "/lambda",
    "queryStringParameters": {
        "query": "1234ABCD"
    },
    "headers": {
        "accept": "text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8",
        "accept-encoding": "gzip",
        "accept-language": "en-US,en;q=0.9",
        "connection": "keep-alive",
        "host": "lambda-alb-123578498.us-east-2.elb.amazonaws.com",
        "upgrade-insecure-requests": "1",
        "user-agent": "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/71.0.3578.98 Safari/537.36",
        "x-amzn-trace-id": "Root=1-5c536348-3d683b8b04734faae651f476",
        "x-forwarded-for": "72.12.164.125",
        "x-forwarded-port": "80",
        "x-forwarded-proto": "http",
        "x-imforwards": "20"
    },
    "body": "",
    "isBase64Encoded": false
}

https://docs.aws.amazon.com/lambda/latest/dg/nodejs-handler.html https://docs.aws.amazon.com/lambda/latest/dg/lambda-services.html

您的案例示例：（注意：查询字符串的名称必须与表达式属性相同）

const queryStringParams = event.queryStringParams;
const updatedQueryStringParams = {};

Object.keys(queryStringParams).forEach(key => updatedQueryStringParams[`:${key}`] = queryStringParams[key]);

    var params = {
        TableName : "Banner",
        KeyConditionExpression: "#od = :year",
        ExpressionAttributeNames:{
            "#od": "order"
        },
        ExpressionAttributeValues: {
            ...updatedQueryStringParams
        }
    };

Answer 3

在使用扫描而不是 KeyConditionExpression 时使用 FilterExpression。 样本

const queryStringParams = event.queryStringParameters;
  let FilterExpression = "";
  let ExpressionAttributeNames = {};
  let ExpressionAttributeValues = {};
  for (const property in queryStringParams) {
    FilterExpression += ` #${property} = :${property} ,`;
    ExpressionAttributeNames["#" + property] = property;
    ExpressionAttributeValues[":" + property] = queryStringParams[property];
  }

  FilterExpression = FilterExpression.slice(0, -1);
  

  const params = {
    TableName: tableName,
    FilterExpression: FilterExpression,
    ExpressionAttributeNames: ExpressionAttributeNames,
    ExpressionAttributeValues: ExpressionAttributeValues
  };