AWS DynamoDB Batch Get Request - iOS

Question

I can perform a simple Get request on a singular table within AWS dynamoDB however when I expand it to a Batch Request across multiple tables I continue to get a error

validation error detected: Value null at 'requestItems.rip.member.keys' failed to satisfy constraint

I understand this as the values not being passed correctly but I can't see what the issue is with my code

//Create Request Values
AWSDynamoDBGetItemInput *getItem = [AWSDynamoDBGetItemInput new];
AWSDynamoDBAttributeValue *hashValue = [AWSDynamoDBAttributeValue new];
hashValue.S = @"User Test";
getItem.key = @{@"ripId": hashValue};

//Create Request Values 2 
AWSDynamoDBGetItemInput *getItem2 = [AWSDynamoDBGetItemInput new];
AWSDynamoDBAttributeValue *hashValue2 = [AWSDynamoDBAttributeValue new];
hashValue2.S = @"User Test";
getItem2.key = @{@"chat": hashValue2};

//Combine to Batch Request
AWSDynamoDBBatchGetItemInput * batchFetch = [AWSDynamoDBBatchGetItemInput new];
batchFetch.requestItems = @{ @"rip": getItem,
                             @"chat": getItem,};

[[dynamoDB batchGetItem:batchFetch] continueWithBlock:^id(BFTask *task) {
    if (!task.error) {

        NSLog(@"BOY SUCCES");

    } else {
        NSLog(@" NO BOY SUCCESS %@",task.error);
    }
    return nil;
}];

Searched the internet high and low but cannot see a working example of a batch request using iOS Objective C (or swift for that matter).

I have tested both variables on a single Get request and they both work.

From what I've read this batch get item can't be used with the AWSDynamoDBObjectMapper? Is there a way mourned this, or does one manually have to iterate through and create the objects form the raw data? — Niklas, Mar 09 '16 at 14:06

score 3 · Accepted Answer · answered May 07 '15 at 18:23

3

You forgot to wrap around AWSDynamoDBAttributeValue in AWSDynamoDBKeysAndAttributes. Here is a simple example from AWSDynamoDBTests.m:

AWSDynamoDBKeysAndAttributes *keysAndAttributes = [AWSDynamoDBKeysAndAttributes new];
keysAndAttributes.keys = @[@{@"hashKey" : attributeValue1},
                           @{@"hashKey" : attributeValue2}];
keysAndAttributes.consistentRead = @YES;

AWSDynamoDBBatchGetItemInput *batchGetItemInput = [AWSDynamoDBBatchGetItemInput new];
batchGetItemInput.requestItems = @{table1Name: keysAndAttributes};

answered May 07 '15 at 18:23

Yosuke

3,759
1
11
21

Out of interest, does a Batch Request accept a `AWSDynamoDBCondition` statement? Currently it isn't for me. – memyselfandmyiphone May 07 '15 at 22:46
[BatchGetItem](http://docs.aws.amazon.com/amazondynamodb/latest/APIReference/API_BatchGetItem.html) does not accept `Condition`. – Yosuke May 08 '15 at 01:00
@memyselfandmyiphone Please can you update your question with the solution ? – iEngineer Sep 17 '15 at 16:27

score 1 · Answer 2 · answered Mar 09 '16 at 15:57

Since the batch get doesn't map to a class I solved it by doing this instead.

I solved it by doing this,

    let dynamoDBObjectMapper = AWSDynamoDBObjectMapper.defaultDynamoDBObjectMapper()
    let task1 = dynamoDBObjectMapper.load(User.self, hashKey: "rtP1oQ5DJG", rangeKey: nil)
    let task2 = dynamoDBObjectMapper.load(User.self, hashKey: "dbqb1zyUq1", rangeKey: nil)

    AWSTask.init(forCompletionOfAllTasksWithResults: [task1, task2]).continueWithBlock { (task) -> AnyObject? in
        if let users = task.result as? [User] {
            print(users.count)
            print(users[0].firstName)
            print(users[1].firstName)
        }
        else if let error = task.error {
            print(error.localizedDescription)
        }
        return nil
    }

@NamanVaishnav Whatever custom class he is mapping to - nothing in particular. — Joshua Wolff, Aug 19 '19 at 07:55

score 0 · Answer 3 · answered Dec 18 '17 at 17:17

Swift 3

I was able to get the BatchGet request work with the following code. Hope this helps someone else who's struggling with the lack of Swift Docs.

This code assumes that you've configured your AWSServiceConfiguration in the AppDelegate application didFinishLaunchingWithOptions method.

let DynamoDB = AWSDynamoDB.default()

    // define your primary hash keys
    let hashAttribute1 = AWSDynamoDBAttributeValue()
    hashAttribute1?.s = "NDlFRTdDODEtQzNCOC00QUI5LUFFMzUtRkIyNTJFNERFOTBF"

    let hashAttribute2 = AWSDynamoDBAttributeValue()
    hashAttribute2?.s = "MjVCNzU3MUQtMEM0NC00NEJELTk5M0YtRTM0QjVDQ0Q1NjlF"

    let keys: Array = [["userID": hashAttribute1], ["userID": hashAttribute2]]

    let keysAndAttributesMap = AWSDynamoDBKeysAndAttributes()
    keysAndAttributesMap?.keys = keys as? [[String : AWSDynamoDBAttributeValue]]
    keysAndAttributesMap?.consistentRead = true
    let tableMap = ["Your-Table-Name" : keysAndAttributesMap]
    let request = AWSDynamoDBBatchGetItemInput()
    request?.requestItems = tableMap as? [String : AWSDynamoDBKeysAndAttributes]
    request?.returnConsumedCapacity = AWSDynamoDBReturnConsumedCapacity.total
    DynamoDB.batchGetItem(request!) { (output, error) in
        if output != nil {
            print("Batch Query output?.responses?.count:", output!.responses!)
        }
        if error != nil {
            print("Batch Query error:", error!)
        }
    }

AWS DynamoDB Batch Get Request - iOS

3 Answers3

Swift 3

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