can't delete object due to foreign key constraint

Question

I\'m trying to do a simple user.destroy but running into the following error:

ERROR: update or delete on table \"users\" violates foreig

Answer 1

An easy solution is to simply cascade-delete the records in the associated table, which can be done through active record, like so:

user.rb

class User < ActiveRecord::Base
  has_many :identities, dependent: :destroy

  # rest of user class
end

Check out the documentation pertaining to has_many for more info.

Answer 2

You would need to remove the Identity that references the user first. Then you can delete the user.. By default the foreign key is doing a restrict so you cannot delete the user if anything references to it.

if you would like use Rails to handle destroying the identity you can do

class User < ActiveRecord::Base
  has_many :identities,  dependent: :destroy 

  ......

 end 

Which would cause Rails to destroy all the dependent records.

But as you are using Foreign keys, you can adjust your migration to set cascade deletes

 add_foreign_key :identities, :users, on_delete: :cascade

Assuming rails 4.2 which has native support