Update ActiveRecord without id column

Question

In a migration is a table without id column created:

create_table :drivers_companies, :id => false do |t|
  t.references :driver
  t.references :company
  t.string :last_sessionid
end

When saving a record:

dc = DriversCompany.where(company_id: 1, driver_id: 5)
if dc.length>0
  dc[0].last_sessionid = req.sessionID
  dc[0].save!
end

I get an error:

Mysql2::Error: Unknown column 'drivers_companies.' in 'where clause': UPDATE 'drivers_companies' SET 'last_sessionid' = 'bth49sv0outsehcg0ribuiu4h' WHERE 'drivers_companies'.'' IS NULL

How to update a record in table without ID column?

Answer 1

ActiveRecord needs a primary key to do this. That can be a problem with legacy tables which can not be changed. You can not solve this without changing the table.

Sometimes one can use the "Composite Primary Keys for ActiveRecords" gem to solve it: https://github.com/composite-primary-keys/composite_primary_keys