`aws dynamodb query` and `aws dynamodb scan` commands are missing docs for the `--limit` parameter

[dead10ck]

Describe the bug

The dynamodb query and dynamodb scan subcommands both seem to respond to a --limit parameter by setting the Limit query parameter as expected; however, --limit is not documented at all in the help pages.

Expected Behavior

--limit should be documented

Current Behavior

It is not

Reproduction Steps

Run aws dynamodb query help

Possible Solution

No response

Additional Information/Context

No response

CLI version used

aws-cli/2.17.26 Python/3.11.9 Linux/6.5.0-45-generic exe/x86_64.ubuntu.22

Environment details (OS name and version, etc.)

Ubuntu 22.04

[RyanFitzSimmonsAK]

Hey @dead10ck, thanks for reaching out. AWS CLI obscures service pagination parameters like --limit in favor of the CLI pagination parameters (--max-items being the analog to --limit). This is done so that pagination in the CLI is consistent between services. However, the service pagination parameters still work, as you mentioned. Please let me know if you have any follow-up questions.

[dead10ck]

But pagination doesn't serve the same purpose as limiting the results of a scan or query. When you --limit a query to 1, you are only charged RCUs for that one row; when you use --max-items, you are charged RCUs for I think the full result set? You can verify by checking the consumed RCUs.

[RyanFitzSimmonsAK]

You should be able to accomplish the same thing using a combination of --max-items and --page-size.

aws dynamodb scan --table-name testTable --limit 1

...
    "Count": 1,
    "ScannedCount": 1,
...

If using only --max-items, all items are scanned as you mentioned. aws dynamodb scan --table-name testTable --max-items 1

...
    "Count": 3,
    "ScannedCount": 3,
    "ConsumedCapacity": null,
    "NextToken": "eyJFeGNsdXNpdmVTdGFydEtleSI6IG51bGwsICJib3RvX3RydW5jYXRlX2Ftb3VudCI6IDF9"

Using both --max-items and page-size correctly restricts the number of scanned and returned items. aws dynamodb scan --table-name testTable --page-size 1 --max-items 1

...
    "Count": 1,
    "ScannedCount": 1,
    "ConsumedCapacity": null,
    "NextToken": "eyJFeGNsdXNpdmVTdGFydEtleSI6IHsiTmFtZSI6IHsiUyI6ICJDYW1teSJ9fX0="

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[dead10ck]

Ah, you are right, thanks! Is that documented anywhere? That doesn't seem like an obvious way to use query limits with the CLI.

[RyanFitzSimmonsAK]

It's explained a bit in the description for page-size.

The size of each page to get in the AWS service call. This does not affect the number of items returned in the command’s output. Setting a smaller page size results in more calls to the AWS service, retrieving fewer items in each call.

--page-size 1 means that it will scan one item at a time until it reaches --max-items total items (in this case also one).