com.amazonaws.services.dynamodbv2.datamodeling.PaginatedScanList Java Examples

/**
 * Find all rows in table given the entity object
 *
 * @return a list of entities found
 * @throws DataAccessException
 */
public List<T> findAll() throws DataAccessException {
    DynamoDBScanExpression dynamoDBScanExpression = new DynamoDBScanExpression();
    DynamoDBMapperConfig config = new DynamoDBMapperConfig(DynamoDBMapperConfig.PaginationLoadingStrategy.EAGER_LOADING);
    PaginatedScanList<T> paginatedScanList = dynamoDBMapper.scan(getType(), dynamoDBScanExpression, config);
    paginatedScanList.loadAllResults();

    List<T> list = new ArrayList<T>(paginatedScanList.size());

    Iterator<T> iterator = paginatedScanList.iterator();
    while (iterator.hasNext()) {
        T element = iterator.next();
        list.add(element);
    }

    return list;
}
 

@Test(enabled = false)
public void testParallelScanPerformance() throws Exception{
    DynamoDBMapper util = TestDynamoDBMapperFactory.createDynamoDBMapper(dynamo);

    DynamoDBScanExpression scanExpression = new DynamoDBScanExpression().withLimit(SCAN_LIMIT);
    scanExpression.addFilterCondition("value", new Condition().withComparisonOperator(ComparisonOperator.NOT_NULL.toString()));
    scanExpression.addFilterCondition("extraData", new Condition().withComparisonOperator(ComparisonOperator.NOT_NULL.toString()));

    long startTime = System.currentTimeMillis();
    PaginatedScanList<SimpleClass> scanList = util.scan(SimpleClass.class, scanExpression);
    scanList.loadAllResults();
    long fullTableScanTime = System.currentTimeMillis() - startTime;
    startTime = System.currentTimeMillis();
    PaginatedParallelScanList<SimpleClass> parallelScanList = util.parallelScan(SimpleClass.class, scanExpression, PARALLEL_SCAN_SEGMENTS);
    parallelScanList.loadAllResults();
    long parallelScanTime = System.currentTimeMillis() - startTime;
    assertTrue(scanList.size() == parallelScanList.size());
    assertTrue(fullTableScanTime > parallelScanTime);
    System.out.println("fullTableScanTime : " + fullTableScanTime + "(ms), parallelScanTime : " + parallelScanTime + "(ms).");
}
 

@Override
public <T> PaginatedScanList<T> scan(Class<T> domainClass,
		DynamoDBScanExpression scanExpression) {
	PaginatedScanList<T> results = dynamoDBMapper.scan(domainClass, scanExpression);
	maybeEmitEvent(new AfterScanEvent<T>(results));
	return results;
}
 

@Override
public Page<T> findAll(Pageable pageable) {

	if (pageable.getSort() != null) {
		throw new UnsupportedOperationException("Sorting not supported for find all scan operations");
	}

	DynamoDBScanExpression scanExpression = new DynamoDBScanExpression();
	// Scan to the end of the page after the requested page
	int scanTo = pageable.getOffset() + (2 * pageable.getPageSize());
	scanExpression.setLimit(scanTo);
	PaginatedScanList<T> paginatedScanList = dynamoDBOperations.scan(domainType, scanExpression);
	Iterator<T> iterator = paginatedScanList.iterator();
	int processedCount = 0;
	if (pageable.getOffset() > 0) {
		processedCount = scanThroughResults(iterator, pageable.getOffset());
		if (processedCount < pageable.getOffset())
			return new PageImpl<T>(new ArrayList<T>());
	}
	// Scan ahead to retrieve the next page count
	List<T> results = readPageOfResults(iterator, pageable.getPageSize());
	
	assertScanEnabled(enableScanPermissions.isFindAllPaginatedScanEnabled(), "findAll(Pageable pageable)");
	assertScanCountEnabled(enableScanPermissions.isFindAllUnpaginatedScanCountEnabled(), "findAll(Pageable pageable)");

	int totalCount = dynamoDBOperations.count(domainType, scanExpression);
	
	return new PageImpl<T>(results, pageable, totalCount);

}
 

public AfterScanEvent(PaginatedScanList<T> source) {
	super(source);
}
 

/**
 * Counts all rows in this specific table.
 * Use it carefully since it loads all results from DynamoDB. To be honest there are only
 * a few situations where this could be considered a wise solution.
 *
 * @return a amount of rows found
 * @throws DataAccessException
 */
public int count() throws DataAccessException {
    DynamoDBScanExpression dynamoDBScanExpression = new DynamoDBScanExpression();
    DynamoDBMapperConfig config = new DynamoDBMapperConfig(DynamoDBMapperConfig.PaginationLoadingStrategy.EAGER_LOADING);
    PaginatedScanList<T> paginatedScanList = dynamoDBMapper.scan(getType(), dynamoDBScanExpression, config);
    paginatedScanList.loadAllResults();
    return paginatedScanList.size();
}
 

public <T> PaginatedScanList<T> scan(Class<T> domainClass,DynamoDBScanExpression scanExpression);