list object v2 - MaxKey, KeyCount , EncodingType

[shirady]

Hi,
A couple of questions about object list V2:

1. Should MaxKey be equal to the integer that was sent with option --max-items ?
2. Should KeyCount be equal to the number of keys in the reply inside content?
3. Should EncodingType be in the response (although it was not specified in the command)?
4. How can we differentiate between a request from the client if he wants the response decoded?
   As I found the query params look the same when we send the command with or without the flag --encoding-type url.

For example I run this command in AWS CLI:
aws s3api list-objects-v2 --bucket shira-test-s3-3 --max-items 2 --debug
The response was with 2 keys only, but the MaxKeyis still 1,000, and the KeyCount is the number of the keys in the bucket (4), but not the number of the keys in the content. EncodingType is url although we didn't specify it in the command.

<ListBucketResult
	xmlns="http://s3.amazonaws.com/doc/2006-03-01/">
	<Name>shira-test-s3-3</Name>
	<Prefix></Prefix>
	<KeyCount>4</KeyCount>
	<MaxKeys>1000</MaxKeys>
	<EncodingType>url</EncodingType>
	<IsTruncated>false</IsTruncated>
	<Contents>
		<Key>asdf%2Bb</Key>
		<LastModified>2022-11-28T07:46:09.000Z</LastModified>
		<ETag>&quot;d41d8cd98f00b204e9800998ecf8427e&quot;</ETag>
		<Size>0</Size>
		<StorageClass>STANDARD</StorageClass>
	</Contents>
	<Contents>
		<Key>foo%2B1%3Abar</Key>
		<LastModified>2022-11-28T07:46:08.000Z</LastModified>
		<ETag>&quot;d41d8cd98f00b204e9800998ecf8427e&quot;</ETag>
		<Size>0</Size>
		<StorageClass>STANDARD</StorageClass>
	</Contents>
	<Contents>
		<Key>foo%3Abar%3Axyzzy</Key>
		<LastModified>2022-11-28T07:46:08.000Z</LastModified>
		<ETag>&quot;d41d8cd98f00b204e9800998ecf8427e&quot;</ETag>
		<Size>0</Size>
		<StorageClass>STANDARD</StorageClass>
	</Contents>
	<Contents>
		<Key>quux+ab%3Athud</Key>
		<LastModified>2022-11-28T07:46:07.000Z</LastModified>
		<ETag>&quot;d41d8cd98f00b204e9800998ecf8427e&quot;</ETag>
		<Size>0</Size>
		<StorageClass>STANDARD</StorageClass>
	</Contents>
</ListBucketResult>'

[tim-finnigan]

Hi @shirady thanks for reaching out. Here is the AWS CLI documentation for the list-objects-v2 command and here is the documentation for the underlying S3 ListObjectsV2 API. For more reference on MaxKeys, KeyCount, and EncodingType:

The --max-items parameter is used for client-side pagination, so it doesn't affect the underlying API request.
Please let us know if you had any follow up questions or you'd like more clarification on anything.

[shirady]

Hi @tim-finnigan,
Thank you for your response, I still have open questions:

1. How the client can limit the MaxKey? (as you answered the flag --max-items is not relevant).
2. In a case where the response has common prefixes - it is not mentioned in the documentation - What should be the keyCount?
3. What is the standard that is used for encoding? (It comes from a certain RFC)
   For example, I saw that the encoded response of space (SP) is '+' but it can be also '%20'.