使用 DynamoDbMapper 从 dynamodb java 检索所有项目 ID

Question

My goal is to retrieve all item's ids. For that, I'm gonna use Java and DynamoDBMapper. The way to do it is to use scan . Right now, my code looks like this:

DynamoDBScanExpression paginatedScanListExpression = new DynamoDBScanExpression()
                .withLimit(10000)
                .withProjectionExpression("id");

var paginatedList = mapper.scanPage(MyObject.class, paginatedScanListExpression);

The problem is that I get only 600 ids per request. I'm aware of a DynamoDB 1MB per query limit, but still, it seems that 600 ids are too little for one request. Does anyone know how I can fetch all the ids more efficiently?

Answer 1

You can try with ScanSpec with ProjectionExpression which specifies the attributes you want in the scan result.

ScanSpec scanSpec = new ScanSpec().withProjectionExpression("id");

    try {
        ItemCollection<ScanOutcome> items = table.scan(scanSpec);

        Iterator<Item> iter = items.iterator();
        while (iter.hasNext()) {
            Item item = iter.next();
            System.out.println(item.toString());
        }

    }
    catch (Exception e) {
        System.err.println("Unable to scan the table:");
        System.err.println(e.getMessage());
    }

Reference - https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/GettingStarted.Java.04.html