How to get column name for primary_key at database level?

I need to get the column name containing the primary key(s) at the database level.

Model.primary_key returns models_id column name which is not the primary key at the database level. I cannot change migrations or modify the tables in anyway.

I can currently get it through the MySqlAdapter with ActiveRecord::Base.connection.primary_key('table_name')

but this does not work with tables that have composite primary keys. If the table contains a composite primary key it returns nil.

Is there any way I can achieve this programatically?