Rails 4 scope adding a null `id` column to result -

i have class this:

class filedownload < activerecord::base   scope :status, -> { select('user_id') } end 

i'm using scope in controller return json response. worked fine in rails 3.2.14. response looked this:

[{ "user_id": 1234 }] 

after upgrading rails 4, response looks this:

[{ "user_id": 1234, "id": null }] 

can explain why null id field being added?

try pluck:

scope :status, -> { pluck(:guid, :status) }