S3 listObjectsV2 - StartAfter does not show intended results

Question

I am trying to get all files in a bucket that come after a certain identifier.

Here is my code, omitted the non-relevant parts.

require_once LIB . DS . 'Aws/vendor/autoload.php';
use Aws\S3\S3Client as S3Client;
use Aws\Credentials as Credentials;

$s3 = new S3Client([
        'region'      => $region,
        'version'     => 'latest',
        'key'    => AWS_KEY,
        'secret' => AWS_SECRET,
        'credentials' => $credentials
    ]
);

$data = $s3->listObjectsV2(
                           [
                               'Bucket' => <MY BUCKET>,
                               // the response content should be after this record
                               'StartAfter' => '302760677',
                               'MaxKeys' => 2
                          ]);
print_r($data);

The result that I am getting is as follows:

Aws\Result Object
(
    [data:Aws\Result:private] => Array
        (
            [IsTruncated] => 1
            [Contents] => Array
                (
                    [0] => Array
                        (
                            [Key] => json/300705/300705046/status.json
                            [LastModified] => Aws\Api\DateTimeResult Object
                                (
                                    [date] => 2018-06-20 11:45:06.000000
                                    [timezone_type] => 2
                                    [timezone] => Z
                                )
                            [ETag] => "2777f5fabc31969108b16cd8459d3b5d"
                            [Size] => 945
                            [StorageClass] => STANDARD
                        )
                    [1] => Array
                        (
                            [Key] => json/300705/300705046/address.json
                            [LastModified] => Aws\Api\DateTimeResult Object
                                (
                                    [date] => 2018-06-20 11:45:06.000000
                                    [timezone_type] => 2
                                    [timezone] => Z
                                )

                            [ETag] => "3fd8ef54a83e93d470f5438079f51345"
                            [Size] => 477
                            [StorageClass] => STANDARD
                        )
                )
        )
)

Here, the response content returned shows data for key - 300705046, which is lesser than what I specified in my "StartAfter" node in the request.

Can anyone help me understand what I might be doing wrong.

Thanks

Answer 1

StartAfter (docs) is matched against the full key.

For example, you might try requesting with:

'StartAfter' => 'json/302760/302760677/address.json',

Answer 2

'StartAfter' will return any keys greater than the value. In your case you set 'StartAfter' to '302760677', which is less than the key 'json/300705/300705046/status.json'. Instead try the following:

'StartAfter' => 'json/302760/302760677'

or

'StartAfter' => 'json/302760/302760677/'

or even

'StartAfter' => 'json/302760/302760677/a'

You might want to use Prefix instead so you don't have to anticipate the exact number of items in the folder. In that case, you would use:

'Prefix' => 'json/302760/302760677/'

If you are explicitly creating s3 folder objects (e.g. 'json/302760/302760677/') and don't want to get that folder object back in your query, you could specify that as both the Prefix and the StartAfter and it would only give you the contents.