Updating an attribute in AWS DynamoDB

Question

Is it not possible to add an attribute in dynamodb dynamically?

I am getting an error saying “The provided key element does not match the schema".

Scenario -

{ id : "123", imageName : "elephant.jpg" }

I want to add an attribute - imagePath : "/path/to/image" to the above data. I used put_item, but it replaces the old item if exists.

Adding an attribute can be achieved using put_item but it will replace the existing item. How can we dynamically add an attribute to the existing data using update_item?

Should I alter the schema of the table with imagePath and then use the update_item function?

Answer 1

Unfortunately, it can't be achieved in a single step. However, it can be achieved in two-step process:-

1) Try to insert the data conditionally i.e. if the key value is already present don't perform any operation (i.e. insert or update - nothing happens)

2) If there is a ConditionalCheckFailedException, then update the item