DynamoDB Advanced Operations using AWS GO SDK

This tutorial helps you to understand and code advanced DynamoDB operations using GO AWS SDK.

• Query
• Query with Filter and Projection
• Get Batch Items
• Paginations

DynamoDB advanced Operations

Table Details:

DynamoDB json:

                            
                            {
                                "userId": {
                                 "S": ""
                                },
                                "firstName": {
                                 "S": ""
                                },
                                "lastName": {
                                 "S": ""
                                },
                                "organization": {
                                 "S": ""
                                }
                            }
                            
                        

DynamoDB Table Item's

GO Code prerequisite

                            
                                region := "ap-south-1"
                                awsSession, _ := session.NewSession(&aws.Config{
                                    Region: aws.String(region)},
                                )
                            
                        

                            
                                dynaClient := dynamodb.New(awsSession)
                            
                        

DynamoDB Query

• Required attribute: Partition key.
Query operation will result all the results with that partition key.

• Optional attribute: Sort key, FilterExpression
Sort key can be used with comparison operator to refine search result.
FilterExpression can be used to filter within result set. However the limit of result set 1MB will be considered before applying the filter.

• Query operation will always return a result set as response. If no matching items are found the result will be empty.

                            
    //Get User details based on Global secondary index
     func GetAdvancedUsers(organization string) ([]UserInfoAdvanced, error) {
    users := []UserInfoAdvanced{}
     tableName := "UserInfo"
    region := "ap-south-1"
     awsSession, _ := session.NewSession(&aws.Config{
     Region: aws.String(region)},
    )
     dynaClient := dynamodb.New(awsSession)
     var queryInput = &dynamodb.QueryInput{
     TableName: aws.String(tableName),
    IndexName: aws.String("organization-index"),
     KeyConditions: map[string]*dynamodb.Condition{ //Only can add sort key, primary key or created index (GSI)
     "organization": {
        ComparisonOperator: aws.String("EQ"),
        AttributeValueList: []*dynamodb.AttributeValue{
         {
        S: aws.String(organization),
        },
        },
        },
        },
        }
                                
        var resp, errQueryDynamoDB = dynaClient.Query(queryInput)
        if errQueryDynamoDB != nil {
        errorString := "Table Lookup Error" + errQueryDynamoDB.Error()
        fmt.Println(errorString)
        return users, errQueryDynamoDB
         }
       
        if len(resp.Items) > 0 {
        errUnMarshal := dynamodbattribute.UnmarshalListOfMaps(resp.Items, &users)
        if errUnMarshal != nil {
        errorString := "Unmarshal users Error" + errUnMarshal.Error()
        fmt.Println(errorString)
        return users, errUnMarshal
        }
        } else {
        errorString := "Users Not found for Organization: " + organization
        fmt.Println(errorString)
        return users, errors.New(errorString)
        }
                                
        fmt.Println("Successfully Fetched " + strconv.FormatInt(*resp.Count, 10) + " results from DynamoDB for Organization: " +
        organization)
                                
         return users, nil
          }
            
        

Input:

Output:

Query with filter and projection

Input:

Output:

Get Batch Items

Limitation: Max 100 Primary Keys

• Can request maximum of 100 items and max size of 16MB.
• If result set is greater than 16MB, the UnprocessedKeys in the response will be non empty.
• If we request more than 100 items ValidationException with the message "Too many items requested for the BatchGetItem call."

Input:

Output:

Paginations

If the result of Query/Scan if greater than 1MB data, we will get only the partial paginated result.

To Get the whole results we need to create input with ExclusiveStartKey. ExclusiveStartKey is the value obtained in result LastEvaluatedKey

                            

	var queryInput = &dynamodb.QueryInput{
		TableName: aws.String(tableName),
		IndexName: aws.String("organization-index"),
		KeyConditions: map[string]*dynamodb.Condition{ //Only can add sort key, primary key or created index (GSI)
			"organization": {
				ComparisonOperator: aws.String("EQ"),
				AttributeValueList: []*dynamodb.AttributeValue{
					{
						S: aws.String(organization),
					},
				},
			},
		},
		ExclusiveStartKey: map[string]*dynamodb.AttributeValue{}, // which is same as LastEvaluatedKey from the initial response
	}