Delete an item in a list of attribute values in a DynamoDB Table - amazon-dynamodb

Question

I need to delete one item from a list in a dynamodb table, but I am getting below error. Could someone help me to resolve it
aws dynamodb delete-item \
--table-name dev-table \
--key '{"Environment":{"S":"all"}}' \
--expression-attribute-names '{"#v": "Values"}' \
--expression-attribute-values '{":vals": {"L": [ { "S": "test"}]}}'
Error:
An error occurred (ValidationException) when calling the DeleteItem operation: ExpressionAttributeNames can only be specified when using expressions

Answer 1

Could not yet figure out how to do it with cli, but here is a lambda that would do this:
import boto3
REGION = 'us-east-1'
dynamodb = boto3.resource('dynamodb', REGION)
env_table = dynamodb.Table('dev-table')
def get_index(totallist):
for item in totallist:
if item['Environment'] == 'all':
index = item['Values'].index('test')
return index
def lambda_handler(event, context):
totallist = env_table.scan()['Items']
index = get_index(totallist)
response = env_table.update_item(
Key={'Environment': 'all'},
UpdateExpression=f"REMOVE #v[{index}]",
ExpressionAttributeNames={'#v': 'Values'},
)
return
Make sure you add an IAM role to the lambda function to allow access to dynamodb.

Answer 2

It sounds like what you need is updateItem. In DynamoDB an item is a record in the table. If you're trying to modify a list within your record, you need to use the UpdateItem request.
Your request should look like below.
aws dynamodb update-item \
--table-name dev-table \
--key '{"Environment":{"S":"all"}}' \
--update-expression "SET Values = :vals" \
--expression-attribute-values '{":vals": {"L": [ { "S": "test"}]}}'
--return-values ALL_NEW
Here's an example request.