DynamodDB: How to update sort key?

Question

The table has two keys: filename (partition key) and eventTime (sort key). I want to update eventTime for certain filename. Tried put_item() and update_item() sending the same filename with new eventTime but those functions add a new item instead of update.

What should I use for that purpose?

Answer 1

You can't. Since it is part of the index, the field is protected. What you should do it to delete the item and add it again with the new sort key.

See https://docs.aws.amazon.com/amazondynamodb/latest/APIReference/API_AttributeValueUpdate.html

Answer 2

According to DynamoDB/AttributeValueUpdate aws docs:

You cannot use UpdateItem to update any primary key attributes. Instead, you will need to delete the item, and then use PutItem to create a new item with new attributes.