incorrect documentation for DynamoDB.Table.update_item()

[altaurog]

Describe the issue

According to the docs for DynamoDB.Table.update_item(), ExpressionAttributeValues must be specified with value types, so: { ":avail":{"S":"Available"}, ":back":{"S":"Backordered"}, ":disc":{"S":"Discontinued"} }
But it doesn’t seem to work this way. The resource interface handles the types automatically, so the code in the example should be { ":avail": "Available", ":back": "Backordered", ":disc": "Discontinued" }
There may be other instances like this, I didn’t check for them.

Links

https://boto3.amazonaws.com/v1/documentation/api/latest/reference/services/dynamodb/table/update_item.html

[adev-code]

Hello @altaurog, thanks for reaching out. I followed the documentation and I did not get any error. Could you please provide a repro code to show this and with full debug logs by adding boto3.set_stream_logger('')? Please redact any sensitive information from the logs. Thanks.

[altaurog]

Here is code to reproduce. First run python mwe.py create to create the table. Then try these combinations:

$ python mwe.py -s
{'PK': {'S': 'b576d3a4-1c89-495b-9b49-5a0e4de462d0'}, 'val': {'N': '1'}}
$ python mwe.py -s -t
{'PK': {'S': 'e48b131a-7ab3-4a42-bb44-32d05b26b23d'}, 'val': {'M': {'N': {'N': '1'}}}}
$ python mwe.py
{'PK': {'S': 'fbc8b13a-df70-49e7-90af-536285bc8c54'}, 'val': {'N': '1'}}
$ python mwe.py -t
Traceback (most recent call last):
  File "/home/altaurog/causematch/code/cm-customdomains/mwe.py", line 55, in <module>
    main(sys.argv[1:])
  File "/home/altaurog/causematch/code/cm-customdomains/mwe.py", line 45, in main
    table.update_item(
  File "/home/altaurog/.venv/cm-customdomains/lib/python3.12/site-packages/boto3/resources/factory.py", line 581, in do_action
    response = action(self, *args, **kwargs)
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/altaurog/.venv/cm-customdomains/lib/python3.12/site-packages/boto3/resources/action.py", line 88, in __call__
    response = getattr(parent.meta.client, operation_name)(*args, **params)
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/altaurog/.venv/cm-customdomains/lib/python3.12/site-packages/botocore/client.py", line 569, in _api_call
    return self._make_api_call(operation_name, kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/altaurog/.venv/cm-customdomains/lib/python3.12/site-packages/botocore/client.py", line 1023, in _make_api_call
    raise error_class(parsed_response, operation_name)
botocore.exceptions.ClientError: An error occurred (ValidationException) when calling the UpdateItem operation: Invalid UpdateExpression: Incorrect operand type for operator or function; operator: ADD, operand type: MAP, typeSet: ALLOWED_FOR_ADD_OPERAND
$ 

I added a -v flag to produce the debug logs, but I don’t have time or confidence to redact the sensitive information right now. Let me know if you have trouble reproducing and perhaps I can include the log later.

# mwe.py
import logging
import sys
import uuid

import boto3

boto3.client("sts").get_caller_identity()
ddb = boto3.resource("dynamodb")
client = boto3.client("dynamodb")

TABLE_NAME = "mwe-d64976ba-fa5f-4fd3-8995-037e8b16b939"


def create_table():
    ddb.create_table(
        TableName=TABLE_NAME,
        BillingMode="PAY_PER_REQUEST",
        AttributeDefinitions=[
            {"AttributeName": "PK", "AttributeType": "S"},
        ],
        KeySchema=[
            {"AttributeName": "PK", "KeyType": "HASH"},
        ],
    )


def main(args):
    if args == ["create"]:
        create_table()
        return

    table = ddb.Table(TABLE_NAME)

    typed = "-t" in args

    if "-v" in args:
        logging.basicConfig(
            filename=f"boto3-ddb-update-item-{typed}.log".lower(),
        )
        boto3.set_stream_logger("")

    one = {"N": 1} if typed else 1
    pk = str(uuid.uuid4())
    expr = "SET val = :one" if "-s" in args else "ADD val :one"
    table.update_item(
        Key={"PK": pk},
        UpdateExpression=expr,
        ExpressionAttributeValues={":one": one},
    )
    res = client.get_item(TableName=TABLE_NAME, Key={"PK": {"S": pk}})
    print(res["Item"])


if __name__ == "__main__":
    main(sys.argv[1:])