Question 18793 in Amazon Web Sevices Question posted in
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DynamoDB / ApiGateWay UpdateItem method returning serializedException – Amazon Web Sevices

Quite new to AWS / DynamoDB. I’m trying to make a UpdateItem method work on my API. I have a Resource with the path x/users/update/{wallet} with wallet being the key.

In here I set a UpdateItem method just like I have all my other Query / Scan / PutItem methods. this has the following mapping template:

{
    "TableName": "Users",
    "KeyConditionExpression": "wallet = :v1",
    "ExpressionAttributeValues": {
        ":v1": {
            "S": "$input.params('wallet')"
        }
        ":v2": {
            "S": $input.json('$.username')
        }
    }
    "UpdateExpression": "set username = :v2",
    "ReturnValues": "UPDATED_NEW"
}

This returns a 200 with "__type": "com.amazon.coral.service#SerializationException"

Pretty sure this is related to my Mapping template but can’t figure out what. Looked at the https://docs.aws.amazon.com/amazondynamodb/latest/APIReference/API_UpdateItem.html and think I used the Sample Request in there as a template to test it like this

{
    "TableName": "Users",
    "Key": {
        "wallet": {
            "S": "$input.params('wallet')"
        },
    },
    "UpdateExpression": "SET username = :val1",
    "ExpressionAttributeValues": {
        ":val1": {
            "S": "$input.path('$.username')"
        },
    },
    "ReturnValues": "ALL_NEW"
}

payload is just as simple as

{"username":"test"}

but that gives the same result.

Any ideas on what i’m doing wrong here?

Cheers!

EDIT:
PutItem looks like this:

{ 
    "TableName": "Users",
    "Item": {
        "userId": {
            "S": "$context.requestId"
        },
        "date": {
            "S": "$input.path('$.date')"
        },
        "wallet": {
            "S": "$input.path('$.wallet')"
        }
    }
}
Tags:

2

Answers


  1. 0

    DynamoDB UpdateItem takes a Key not a KeyConditionExpression

    This one below is correct:

    {
"TableName": "Users",
"Key": {
    "wallet": {
        "S": "$input.params('wallet')"
    },
},
"UpdateExpression": "SET username = :val1",
"ExpressionAttributeValues": {
    ":val1": {"S": "$input.params('$.username')"},
},
"ReturnValues": "ALL_NEW"
}

    You also state your payload is simply

    {"username":"test"}

    You must also specify wallet as this is the key

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  2. 0

    It looks like you’re not accessing the record to update with the key of your table. Unlike SQL, you cannot access a record to update with any field in DynamoDB. You have to use your key depending on how you defined it (PK or PK + SK).

    Given that you have both PK and SK defined, you need them both in your key input. Together they form a composite primary key. The below input should work for you.

    {
    "TableName": "Users",
    "Key": {
        "wallet": {
            "S": "$input.params('wallet')"
        },
        "date": {
            "S": "$input.params('date')"
        },
    },
    "UpdateExpression": "SET username = :val1",
    "ExpressionAttributeValues": {
        ":val1": {
            "S": "$input.path('$.username')"
        },
    },
    "ReturnValues": "ALL_NEW"
}
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