DynamoDB-删除表达式

语法：

  1. [Remove action[,action]...]——从项目中删除属性
  2. [DELETE action[,action]...]——从集合中删除元素/项目
  • 删除项目

您可以使用 delete 方法，通过指定项目的主键来删除一个项目。您可以提供一个 ConditionExpression 以防止在不符合条件时删除项目。

  var AWS = require('aws-sdk');
  var fs = require('fs');
  var uuid = require('uuid');
  
  AWS.config.update({
      region: "us-west-2",
      endpoint: "http://dynamodb:8000"
  })
  
 var docClient = new AWS.DynamoDB.DocumentClient();
 
 exports.handler = async function( event, context, callback ){

     response = {
         headers: { 
             "Content-Type": 'application/json',
             "Access-Control-Allow-Origin": "*",
             "Access-Control-Allow-Credentials": true,
             "Access-Control-Allow-Headers": "Content-Type, Access-Control-Allow-Headers, Access-Control-Allow-Origin, Authorization, X-Requested-With"
         },
     }
 
    case 'DELETE': {
             var table ='book_table', hash = 'book';
             id = 'bee1bea0-4b6a-4fbc-8cf0-8c030519c909';
             var params = {
                 TableName: table,
                 Key: {
                     "hash": hash,
                     "id": id
                 },
 
                 ConditionExpression: "price < :h",
                 ExpressionAttributeValues: {":h" : 50},
                 await docClient.delete( params ).promise().then(
                 ( data ) => {
                     response.body = JSON.stringify({"success": data});
                     console.log("success", data );
                     
                 }
             ).catch(
                ( err ) =>{
                     console.log("error", err );
                     response.statusCode = err.statusCode;
                     response.body = JSON.stringify({"error": err});
                 }
             );
             callback( null, response );
             break;
         }}
  • 添加集合
 1 var AWS = require('aws-sdk');
 2 var fs = require('fs');
 3 var uuid = require('uuid');
 4 
 5 AWS.config.update({
 6     region: "us-west-2",
 7     endpoint: "http://dynamodb:8000"
 8 })
 9 
10 var docClient = new AWS.DynamoDB.DocumentClient();
11 
12 exports.handler = async function( event, context, callback ){
13 
14     response = {
15         headers: { 
16             "Content-Type": 'application/json',
17             "Access-Control-Allow-Origin": "*",
18             "Access-Control-Allow-Credentials": true,
19             "Access-Control-Allow-Headers": "Content-Type, Access-Control-Allow-Headers, Access-Control-Allow-Origin, Authorization, X-Requested-With"
20         },
21     }
22     
23     case 'POST': {
24             var table = "book_table", hash = "test";
25 
26             var params = {
27                 TableName: table,
28                 Item: {
29                     "hash": hash,
30 
31                     "id": uuid(),
32 
33                     "book_type": docClient.createSet(["青春文学", "历史典故", "杂志", "小说"])
34         }
35     
36                     };
37             await docClient.put( params ).promise().then(
38                 ( data ) => {
39                     response.body = JSON.stringify({"success": data})
40                 }
41             ).catch(
42                 ( err ) =>{
43                     response = {
44                         statusCode: err.statusCode,
45                         body: JSON.stringify({
46                             code: err.code,
47                             message: err.message
48                         })
49                     }
50                 }
51             )
52          
53             callback( null, response );
54             break;
55         }
56 }

程序运行成功后返回：

 1 {
 2     "success:": {
 3         "Attributes": {
 4             "book_type": {
 5                 "wrapperName": "Set",
 6                 "values": [
 7                     "历史典故",
 8                     "小说",
 9                     "青春文学"，        
10                     “杂志”
11                 ],
12                 "type": "String"
13             },
14             "hash": "test",
15             "id": "87de4a25-7361-4fcf-af01-5949c55099a3"
16         }
17     }
18 }
View Code
 
  • 从集合中删除项目
 1 var AWS = require('aws-sdk');
 2 var fs = require('fs');
 3 var uuid = require('uuid');
 4 
 5 AWS.config.update({
 6     region: "us-west-2",
 7     endpoint: "http://dynamodb:8000"
 8 })
 9 
10 var docClient = new AWS.DynamoDB.DocumentClient();
11 
12 exports.handler = async function( event, context, callback ){
13 
14     response = {
15         headers: { 
16             "Content-Type": 'application/json',
17             "Access-Control-Allow-Origin": "*",
18             "Access-Control-Allow-Credentials": true,
19             "Access-Control-Allow-Headers": "Content-Type, Access-Control-Allow-Headers, Access-Control-Allow-Origin, Authorization, X-Requested-With"
20         },
21     }
22             case 'PUT': {
23             var table = 'book_table', hash = 'test';
24             var id = "87de4a25-7361-4fcf-af01-5949c55099a3";
25             var params = {
26                 TableName: table,
27                 Key: {
28                     "hash": hash,
29                     "id": id
30                 },
31 
32                 UpdateExpression: "DELETE book_type :value",
33                 ExpressionAttributeValues: {
34                     ":value": docClient.createSet(["杂志"])
35                 },
36                 ReturnValues: "ALL_NEW"
37             };
38 
39            await docClient.update( params ).promise().then(
40                 ( success ) => {
41                     response.body = JSON.stringify({ "success:": success })
42                 }
43                
44             ).catch(
45                 ( err ) => {
46                     console.log(err);
47                     response.statusCode = err.statusCode;
48                     response.body = JSON.stringify({
49                         code: err.code,
50                         message: err.message
51                     })
52                 }
53             );
54             callback( null, response );
55             break;
56         };}

程序运行成功后返回：

    •  1 {
 2     "success:": {
 3         "Attributes": {
 4             "book_type": {
 5                 "wrapperName": "Set",
 6                 "values": [
 7                     "历史典故",
 8                     "小说",
 9                     "青春文学"
10                 ],
11                 "type": "String"
12             },
13             "hash": "test",
14             "id": "87de4a25-7361-4fcf-af01-5949c55099a3"
15         }
16     }
17 }
      View Code
  • 从项目中删除属性

　　

 1 var AWS = require('aws-sdk');
 2 var fs = require('fs');
 3 var uuid = require('uuid');
 4 
 5 AWS.config.update({
 6     region: "us-west-2",
 7     endpoint: "http://dynamodb:8000"
 8 })
 9 
10 var docClient = new AWS.DynamoDB.DocumentClient();
11 
12 exports.handler = async function( event, context, callback ){
13 
14     response = {
15         headers: { 
16             "Content-Type": 'application/json',
17             "Access-Control-Allow-Origin": "*",
18             "Access-Control-Allow-Credentials": true,
19             "Access-Control-Allow-Headers": "Content-Type, Access-Control-Allow-Headers, Access-Control-Allow-Origin, Authorization, X-Requested-With"
20         },
21     }
22     case 'PUT': {
23             var table = 'book_table', hash = 'test';
24             var id = "556433cf-37b6-4e12-b513-9c261fd279f7";
25             var params = {
26                 TableName: table,
27                 Key: {
28                     "hash": hash,
29                     "id": id
30                 },
31                 UpdateExpression: "REMOVE price",
32 
33     
34                ReturnValues: "ALL_NEW"
35             };
36 
37            await docClient.update( params ).promise().then(
38                 ( success ) => {
39                     response.body = JSON.stringify({ "success:": success })
40                 }
41                
42             ).catch(
43                 ( err ) => {
44                     console.log(err);
45                     response.statusCode = err.statusCode;
46                     response.body = JSON.stringify({
47                         code: err.code,
48                         message: err.message
49                     })
50                 }
51             );
52             callback( null, response );
53             break;
54         };
55 }

程序运行成功后返回：

 1             {
 2                     "success:": {
 3                         "Attributes": {
 4                             "booktype": [
 5                                 "青春文学",
 6                                 "历史典故",
 7                                 "读者杂志",
 8                                 "最小说",
 9                                 "科技畅想",
10                                 "穿越时空"
11                             ],
12                             "hash": "book",
13                             "id": "556433cf-37b6-4e12-b513-9c261fd279f7"
14                         }
15                     }
16                 }
View Code

 ps: 本文为本人原创文章，若有疑问，欢迎下方留言，也可自读aws的相关api文档： https://docs.aws.amazon.com/zh_cn/amazondynamodb/latest/developerguide/Expressions.OperatorsAndFunctions.html

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原文地址：https://www.cnblogs.com/landen/p/9815109.html