Oracle provides many good subject areas and fact tables in the Autonomous Data Warehouse. If I need to provide additional custom "fields", I can create a custom extended dim and join the extended dim to an out-of-the-box dim, allowing you to pull in those custom columns into an existing subject area on a dimension.

Is there a way to do this for a fact table—an extended fact? We know that you can create some "calculated"/derived objects in the Semantic model for the Fact table, but there are two concerns with this approach. 1) We we have some complex calculations that we want to store in the database itself. 2) running complex calculations as a "calculated"/derived object in the semantic model happen at runtime, so performance on the query is slower.