Data teams often maintain uniqueness guarantees in their pipelines, but without a flexible way to represent all of them in the table schema, users and tools cannot discover them and the query optimizer cannot safely leverage them. Business entities often have more than one value, or combination of values, known to be unique: a users table might use user_id as its primary row identifier while its data model also records separate uniqueness guarantees for username, an email address, and (workspace_id, external_user_id).