Can I ask why you are prefixing all of your column names with user_ ? They’re already on a table named users. users.user_whatever just seems repetitive.
Setting that aside, the error explains the reason. You say that has_one :tournaments_game, Tournament in your User schema, this requires that the tournaments table has a column that points to the users table. By default that column would be named #{schema_name}_#{primary_key} which for you is user_user_id.
