Using DynamoDB's updateItem with a numeric value

Question

I am trying to update a record in DynamoDB using updateItem as part of version 3 of the PHP AWS SDK.

The field I am trying to update should contain a numeric value.

If I run this code I get an error:

$params = array(
    'TableName' => $table,
    'Key' => array('id' => array('S' => $id) ),
    'UpdateExpression' => 'set newField = :val',
    'ExpressionAttributeValues' => array(
        ':val'  => array('N' => 99)
    ),
    'ReturnValues' => 'ALL_NEW'
);

print_r($params);

$result = $client->updateItem($params);

Error:

Client error: `POST https://dynamodb.eu-west-2.amazonaws.com` resulted in a `400 Bad Request` 
response: {"__type":"com.amazon.coral.service#SerializationException","Message":"NUMBER_VALUE cannot be converted to String"}

But if I amend:

':val'  => array('N' => 99)

To be:

':val'  => array('N' => "99")

Or

':val'  => array('N' => (string)99)

Then the request is successful and Dynamo is updated. If I go to the Dynamo console then I can see the updated record and the field correctly shows as a Number type.

Is there a better way to handle the process of updating DynamoDB records with integers, casting as a string so that the PHP SDK works doesn't seem like the best approach?

jarmod · Accepted Answer · 2020-10-16 22:39:16Z

3

All DynamoDB SDKs afaik originally expected numeric values to be presented as strings, but subsequently various marshaling enhancements have brought native type support.

I don't use PHP, but see DynamoDB JSON and Array Marshaling for PHP.

answered Oct 16, 2020 at 22:39

jarmod

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