节点。js AWS dynamodb updateItem

Question

有没有办法通过updateItem实现以下几点：1。如果DynamoDB 2中不存在属性，则添加属性。如果DynamoDB 3中存在属性，则更新属性。如果参数中不包含这些属性，请保持这些属性不变。

下面是一个例子：这是DynamoDB中的对象：

{
    id: "1234",
    variable1: "hello",
    variable2: "world"
}

以下是我想更新的输入：

{
    id: "1234",
    variable1: "hello2",
    variable23: "dog"  // the variable name "variable23" could be anything
}

下面是我想要实现的DynamoDB中的更新项：

{
    id: "1234",
    variable1: "hello2",
    variable2: "world",
    variable23: "dog"
}

“variable23”可以是任何变量名作为输入。

请帮忙！我使用node。js，如果有人能给我展示一些代码来实现这一点，我真的很感激。

谢谢

Answer 1

这里有一个更安全和最新的功能来实现这一点：

const {
  DynamoDBClient, UpdateItemCommand,
} = require('@aws-sdk/client-dynamodb');
const { marshall, unmarshall } = require('@aws-sdk/util-dynamodb');

const client = new DynamoDBClient({});

/**
 * Update item in DynamoDB table
 * @param {string} tableName // Name of the target table
 * @param {object} key // Object containing target item key(s)
 * @param {object} item // Object containing updates for target item
 */
const update = async (tableName, key, item) => {
  const itemKeys = Object.keys(item);

  // When we do updates we need to tell DynamoDB what fields we want updated.
  // If that's not annoying enough, we also need to be careful as some field names
  // are reserved - so DynamoDB won't like them in the UpdateExpressions list.
  // To avoid passing reserved words we prefix each field with "#field" and provide the correct
  // field mapping in ExpressionAttributeNames. The same has to be done with the actual
  // value as well. They are prefixed with ":value" and mapped in ExpressionAttributeValues
  // along witht heir actual value
  const { Attributes } = await client.send(new UpdateItemCommand({
    TableName: tableName,
    Key: marshall(key),
    ReturnValues: 'ALL_NEW',
    UpdateExpression: `SET ${itemKeys.map((k, index) => `#field${index} = :value${index}`).join(', ')}`,
    ExpressionAttributeNames: itemKeys.reduce((accumulator, k, index) => ({ ...accumulator, [`#field${index}`]: k }), {}),
    ExpressionAttributeValues: marshall(itemKeys.reduce((accumulator, k, index) => ({ ...accumulator, [`:value${index}`]: item[k] }), {})),
  }));

  return unmarshall(Attributes);
};

Answer 2

可以动态更新属性。请参阅下面的代码。

export const update = (item) => {
  console.log(item)
  const Item = {
    note: "dynamic",
    totalChild: "totalChild",
    totalGuests: "totalGuests"
  };
  let updateExpression='set';
  let ExpressionAttributeNames={};
  let ExpressionAttributeValues = {};
  for (const property in Item) {
    updateExpression += ` #${property} = :${property} ,`;
    ExpressionAttributeNames['#'+property] = property ;
    ExpressionAttributeValues[':'+property]=Item[property];
  }

  
  console.log(ExpressionAttributeNames);


  updateExpression= updateExpression.slice(0, -1);
  
  
   const params = {
     TableName: TABLE_NAME,
     Key: {
      booking_attempt_id: item.booking_attempt_id,
     },
     UpdateExpression: updateExpression,
     ExpressionAttributeNames: ExpressionAttributeNames,
     ExpressionAttributeValues: ExpressionAttributeValues
   };

   return dynamo.update(params).promise().then(result => {
       return result;
   })
   
}

Answer 3

这正是AWS所说的。DynamoDB。DocumentClient的更新方法不起作用。

关于如何在节点中使用AWS SDK for JavaScript的更新方法，这里已经有一个示例代码。js。

例如：

'use strict';

const aws = require('aws-sdk');

// It is recommended that we instantiate AWS clients outside the scope of the handler 
// to take advantage of connection re-use.
const docClient = new aws.DynamoDB.DocumentClient();

exports.handler = (event, context, callback) => {
    const params = {
        TableName: "MYTABLE",
        Key: {
            "id": "1"
        },
        UpdateExpression: "set variable1 = :x, #MyVariable = :y",
        ExpressionAttributeNames: {
            "#MyVariable": "variable23"
        },
        ExpressionAttributeValues: {
            ":x": "hello2",
            ":y": "dog"
        }
    };

    docClient.update(params, function(err, data) {
        if (err) console.log(err);
        else console.log(data);
    });
};