How to Query DynamoDB when Range key is unknown

Question

I have a table with the following KeySchema:

KeySchema: [
{AttributeName: USER_ID,KeyType: HASH}, 
{AttributeName: COMPLETED,KeyType: RANGE}],

The user ID is just a integer, but COMPLETED is a timestamp of when the record was created.

I'm trying to retrieve a record with this code:

Item item = tbl.getItem("USER_ID", "4216634082");

But I get this error:

AmazonDynamoDBException: The provided key element does not match the schema (Service: AmazonDynamoDBv2; Status Code: 400; Error Code: ValidationException...

Since the range key is a timestamp, I have no idea what it is until I've already found the record. How do I achieve this?

Answer 1

You are calling getItem, which is a lookup of an item by its key - this requires both hash and range components if the key schema defines both.

If you want to get all the items that have a particular hash (ordered by range key), you need to use a query. For example:

Table table = dynamoDB.getTable("YourTable");

QuerySpec spec = new QuerySpec()
    .withKeyConditionExpression("USER_ID = :user_id")
    .withValueMap(new ValueMap()
        .withString(":user_id", "4216634082"))

ItemCollection<QueryOutcome> items = table.query(spec);

See http://docs.aws.amazon.com/amazondynamodb/latest/developerguide/QueryAndScan.html for concepts and http://docs.aws.amazon.com/amazondynamodb/latest/developerguide/QueryingJavaDocumentAPI.html for detailed Java SDK documentation.

(Example lifted from the doc links)