How to do Query in DynamoDB on the basis of HashKey and range Key?

Question

I am new to DynamoDb stuff. I just want to know how can we query on a table in DynamoDB with the hashKey and rangeKey.

Let's say my Table is TestTable and it's schema is something like this:

1.Id (HK of type String)
2 Date (RK of type String )
3 Name (attribute of type String)

Now If I want to query on this table on the basis of hashKey which is Id here, we make a query as :

Let's say my query is to get all Items having Id ="123".

TestTable testTable = new TestTable();
testTable.setId("123");

DynamoDBQueryExpression<TestTable> queryExpression = new DynamoDBQueryExpression<TestTable>()
                                                                .withHashKeyValues(TestTable)
                                                                .withConsistentRead(false);

Now I want to get all Items having Id ="123" and Date ="1234".

How can I query this thing in DynamoDB

I am using java as my programming language.

Markus Klems · Accepted Answer · 2015-06-15 09:42:45Z

16

I wrote an article about DynamoDB queries and indexing using the AWS Java SDK some time ago: http://labs.journwe.com/2013/12/15/dynamodb-secondary-indexes/

In your case, it should work like this (see http://docs.aws.amazon.com/amazondynamodb/latest/developerguide/JavaQueryScanORMModelExample.html):

AmazonDynamoDBClient client = new AmazonDynamoDBClient(new ProfileCredentialsProvider());
DynamoDBMapper mapper = new DynamoDBMapper(client);

String hashKey = "123";
long twoWeeksAgoMilli = (new Date()).getTime() - (15L*24L*60L*60L*1000L);
Date twoWeeksAgo = new Date();
twoWeeksAgo.setTime(twoWeeksAgoMilli);
SimpleDateFormat dateFormatter = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSS'Z'");
dateFormatter.setTimeZone(TimeZone.getTimeZone("UTC"));
String twoWeeksAgoStr = dateFormatter.format(twoWeeksAgo);            
Condition rangeKeyCondition = new Condition()
        .withComparisonOperator(ComparisonOperator.GT.toString())
        .withAttributeValueList(new AttributeValue().withS(twoWeeksAgoStr.toString()));

Reply replyKey = new Reply();
replyKey.setId(hashKey);

DynamoDBQueryExpression<Reply> queryExpression = new DynamoDBQueryExpression<Reply>()
        .withHashKeyValues(replyKey)
        .withRangeKeyCondition("ReplyDateTime", rangeKeyCondition);

List<Reply> latestReplies = mapper.query(Reply.class, queryExpression);

Check out the Java Object Persistence Model section of the DynamoDB docs for more info.

answered Jun 15, 2015 at 9:42

Markus Klems

4942 silver badges6 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

Geek_To_Learn Over a year ago

Hey.. I have read your article already... It is indeed a nice one.Actually I don't want to make such condition for range key operation. Isn't there any other way ?

Markus Klems Over a year ago

The other possibibility that I see (but have not tried, yet) is to use the low-level Java query api: docs.aws.amazon.com/amazondynamodb/latest/developerguide/…

QuerySpec().withKeyConditionExpression("Id = :v_id and Date = :v_date").withValueMap(new ValueMap().withString(":v_id", "123") .withString(":v_date", "1234")

8bitjunkie Over a year ago

If you're the author of the article, please can you fix the broken link?

Nikita · Accepted Answer · 2017-08-27 12:25:22Z

8

You could use dynamoDbMapper.load() as following:

TestTable testTable = new TestTable();
testTable.setId("123");
testTable.setDate("1234");
TestTable result = dynamoDBMapper.load(testTable);

answered Aug 27, 2017 at 12:25

Nikita

3651 gold badge4 silver badges10 bronze badges

1 Comment

Tino Over a year ago

What is returned when the value is not found on the table? Anyone knows?

Mingliang Liu · Accepted Answer · 2015-06-18 19:56:14Z

3

If you're not using index, you should have exact one item, if any, whose Id ="123" and Date ="1234".

For the exact hash key and range key (in case of = operator), you don't need a query operation. Please have a loot at GetItem API, which is nifty. See documentation page.

And if you need non-EQ operator for range key (e.g. >=), you can use key condition expression in Query operation: Id = :id and Date >= :date.

answered Jun 18, 2015 at 19:56

Mingliang Liu

5,8071 gold badge20 silver badges13 bronze badges

Collectives™ on Stack Overflow

How to do Query in DynamoDB on the basis of HashKey and range Key?

3 Answers 3

3 Comments

1 Comment

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

3 Comments

1 Comment

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related