Question

I have a Rails 3.1 app with a User model and a Venue model. These two models have a HABTM relationship – A user may manage many venues and a venue may be managed by many users.

I’d like users to be able to select a default venue so I’m trying to add a default_venue_id attribute to User with the following migration:

class AddDefaultVenueIdToUser < ActiveRecord::Migration
  def self.up
    add_column :users, :default_venue_id, :integer
  end

  def self.down
    remove_column :users, :default_venue_id
  end
end

The problem is that when I run that migration against my PostgreSQL database, it’s assuming that default_venue_id is the foreign key for a relationship with the non-existent default_venues table and throws the following error:

PGError: ERROR:  relation "default_venues" does not exist
: ALTER TABLE "users" ADD FOREIGN KEY ("default_venue_id") REFERENCES "default_venues" ("id")

Should I be doing something to tell the database that I’m not trying to create a relationship or am I going about this the wrong way?

Edit: I’ve just realised that another developer who worked on the project added the schema_plus gem which automatically defines constraints for columns ending in _id

That explains why I’ve never run into this behaviour before!

Answer 1

It would be helpful to see the Models as well to diagnose this problem.

However with that being said, I think that if you are using HABTM associations here it might be a good idea to take a look at a has many through relationship. example: VenueManagement which would have your user_id and venue_id. That way you could handle extra attributes on the association where it makes sense, like a default flag.

Hope that helps.