DynamoDB - UpdateItem where X <= Y - amazon-dynamodb

Question

I have a DynamoDb table defined with a composite key of
$response = $this->dynamoDb->createTable([
...
'KeySchema' => [
[
'AttributeName' => 'product_code',
'KeyType' => 'HASH'
],
[
'AttributeName' => 'token',
'KeyType' => 'RANGE'
]
]
...
]);
I want to be able to update all records where "product_code" = "X" and "created_at" <= "Y". I assume it must be possible but I am a bit stumped. The updateItem method requires the full key but I want a conditional update without specifying a key. My latest stub reads as
$response = $this->dynamoDb->updateItem([
'TableName' => 'products',
'ExpressionAttributeValues' => [
':val1' => ['N' => (string)$this->input['product_code']]
':val2' => ['N' => (string)$this->product['created_at']['N']],
':val3' => ['N' => (string)strtotime("now")],
],
'ConditionExpression' => 'product_code = :val1 AND processed_at <= :val2',
'UpdateExpression' => 'set processed_at = :val3'
]);
But the generated error message reads as follows:
[Key] is missing and is a required parameter
Which command should I be using? Any help building my query is greatly appreciated.

Answer 1

The following is taken from AWS DynamoDB API reference for UpdateItem:
For the primary key, you must provide all of the attributes. For example, with a simple primary key, you only need to provide a value for the partition key. For a composite primary key, you must provide values for both the partition key and the sort key.
In your code (the update item part) you provide only hash key (product_code). You have to provide the range key (token) as well in your ConditionExpression property, because you defined a composite key.
EDIT:
(regarding the comment)
The following describes the parameters for UpdateItem:
Request Parameters
...
Key
The primary key of the item to be updated. Each element consists of an
attribute name and a value for that attribute.
For the primary key, you must provide all of the attributes. For
example, with a simple primary key, you only need to provide a value
for the partition key. For a composite primary key, you must provide
values for both the partition key and the sort key.
Type: String to AttributeValue object map
Required: Yes
...
As you can see, the primary key is required for an UpdateItem operation.
So you cannot use a secondary index to point UpdateItem to a collection of items to update.
However, you can query the table by a secondary index, and collect the primary keys of the resulted items, say in an array keysToUpdate.
Then you can update the desired items, whose keys are in keyToUpdate.