How to sort DynamoDB Hashkey in ascending order in Android

Question

I'm working on an Android application where I'm creating a DynamoDB table with a "Number" Hashkey.

public static void createTable() {

    Log.d(TAG, "Create table called");

    AmazonDynamoDBClient ddb = UserPreferenceDemoActivity.clientManager
            .ddb();

    KeySchemaElement kse = new KeySchemaElement().withAttributeName(
            "Tid").withKeyType(KeyType.HASH);
    AttributeDefinition ad = new AttributeDefinition().withAttributeName(
            "Tid").withAttributeType(ScalarAttributeType.N);

    ProvisionedThroughput pt = new ProvisionedThroughput()
            .withReadCapacityUnits(10l).withWriteCapacityUnits(5l);

    CreateTableRequest request = new CreateTableRequest()
            .withTableName(Constants.TEST_TABLE_NAME)
            .withKeySchema(kse).withAttributeDefinitions(ad)                               
            .withProvisionedThroughput(pt);

    try {
        Log.d(TAG, "Sending Create table request");
        ddb.createTable(request);
        Log.d(TAG, "Create request response successfully recieved");
    } catch (AmazonServiceException ex) {
        Log.e(TAG, "Error sending create table request", ex);
        UserPreferenceDemoActivity.clientManager
                .wipeCredentialsOnAuthError(ex);
    }
    insertUsers();
}

I'm then calling the insertUsers() method in the end, where I'm adding three Key values (800,815,830) into the created table:

 public static void insertUsers() {
    AmazonDynamoDBClient ddb = UserPreferenceDemoActivity.clientManager
            .ddb();
    DynamoDBMapper mapper = new DynamoDBMapper(ddb);

    try {
        for (int i = 1; i <= 3; i++) {
            UserPreference userPreference = new UserPreference();

            if (i == 1)
            {
             userPreference.setTid(800);                 
            }
            else if (i == 2)
            {
                userPreference.setTid(815); 
            }
            else
            {
                userPreference.setTid(830);                     
            }

            Log.d(TAG, "Inserting Tid and Dage");
            mapper.save(userPreference);
            Log.d(TAG, "Tid and Dage inserted");
        }
    } catch (AmazonServiceException ex) {
        Log.e(TAG, "Error inserting users");
        UserPreferenceDemoActivity.clientManager
                .wipeCredentialsOnAuthError(ex);
    }
}

But the ordering in AWS DynamoDB Service is:

enter image description here

How do I sort the table in ascending order, so I can obtain the ordering like : 800,815,830

Chen Harel · Accepted Answer · 2015-01-10 15:25:41Z

2

Hash isn't ordered in DynamoDB. Your only workaround here is to Scan the whole table to code and sort in the application layer.

answered Jan 10, 2015 at 15:25

Chen Harel

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Comments

kaseOga · Accepted Answer · 2015-01-12 08:19:18Z

0

From AWS Documentation:

DynamoDB builds an unordered hash index on the hash primary key attribute and a sorted range index on the range primary key attribute

Hope it help,

answered Jan 12, 2015 at 8:19

kaseOga

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