node.js - 如何使用 AWS Lambda 按名称查询 dynamoDB 表

Question

我有 dynamoDB 表，

表名xx

主分区键id(数字)

主排序键名称(字符串)

我想通过name查询它。

'use strict';
const AWS = require("aws-sdk");
const dynamodb = new AWS.DynamoDB();
const docClient = new AWS.DynamoDB.DocumentClient();

exports.handler = function(event, ctx, callback) {

    var params = {
          TableName: 'xx',

            KeyConditionExpression: "#name = :name",
                 ExpressionAttributeNames:{
            "#name": "name"
        },
                     ExpressionAttributeValues: {
            ":name":event.name
        }
    };

    docClient.query(params, function(err, data){
        if(err){
            callback(err, null);
        }else{
            callback(null, data);
        }
    });
}

但我收到一个错误，名为:“查询条件缺少关键模式元素:id:”如何处理？

Answer 1

DynamoDB 是一个 NoSQL 数据库，因此默认情况下您只能查询主键。您有几个选择:

• 创建全局二级索引并针对该索引进行查询 (Link):

  "A global secondary index contains a selection of attributes from the base table, but they are organized by a primary key that is different from that of the table. The index key does not need to have any of the key attributes from the table; it doesn't even need to have the same key schema as a table."

• 扫描而不是查询:

  var params=  {
      TableName:'xx',
      ProjectionExpression:'name', // remove this string if you want to get not only 'name'
      FilterExpression:'name = :name',
      ExpressionAttributeValues:{ ":name" : event.name }
  };
  
  docClient.scan(params, function(err, data){
      if(err){
          callback(err, null);
      }else{
          callback(null, data);
     }
  });
  

如果您的表格不会很大，扫描是更简单、更便宜的方法(我相信全局二级指数有相关成本)，但“正确”的方法是使用全局二级指数。