Storing an List of Objects in DynamoDB and retrieving them partially

Question

This might two separate questions into a single one. But that's my current use case. I have a POJO which has specific attributes.

It might look like:

class MyObject {
    String id;
    String name;
    int size;

getters and setters () ....
}

Now I have a list of these objects - List which I wish to store in a single in Dynamo. Something like

RecordID            Attributes
abcd123             List<MyObject>

Can I store the data in Dynamo in the above format? My second question is related to the above use case.

Now that I have stored the records, can I retrieve a specific part of the List? Like, I want indices 0 - 5 to be returned from the DyanmoDBQuery Request and not the entire list itself.

Is that possible?

I am pretty new to DynamoDB and I am not sure how well there is support for storing custom objects in Dynamo.

Answer 1

If you are able to massage your schema and move to a Partition-Sort key schema, where the Partition key is RecordID and the Sort key is ItemNumber, where Item number is the index of each MyObject in the abcd123 list above, then you can get sublists with a range query:

Item example:

RecordID (partition key) asdfasdfadsf
ItemNumber (sort key)    0
Item                     an instance of MyObject

Range query parameters:

KeyCondition: RecordId = :rid AND ItemNumber BETWEEN :lower AND :upper
ExpressionAttributeValues = { ":rid": "asdfasdfasdf", ":lower": 0, ":upper": 5 }

Note that the :upper bound is inclusive, so the query example above will return MyObjects with RecordId=asdfasdfasdf with ItemNumbers 0, 1, 2, 3, 4, and 5.