I am trying to add a primary key constraint to an existing table, and I get the following error;

Cannot create or update table because the child column(s) `my_primary_key` of primary key `pk` cannot be set to nullable. Either drop the constraint, or change the column nullability.

This doesn't make sense to me... why would you want a primary key column to be nullable? In any event, I tried to alter the column to allow nulls and still got the same error.

I appreciate that primary keys and foreign keys in data bricks are informational only, but I want to be able to support downstream BI developers with this information if possible.