When using Postgres Enum types with Rails, specifying CREATE TYPE xyz_setting AS ENUM in your migration breaks your db/schema.rb file

Question

this is based on some dev.to articles here https://dev.to/diegocasmo/using-postgres-enum-type-in-rails-30mo and here https://dev.to/amplifr/postgres-enums-with-rails-4ld0 and the same guy's article here https://medium.com/@diegocasmo/using-postgres-enum-type-in-rails-799db99117ff

If you follow the advice above, you are advised to create a Rails schema migration for your Postgres backed schema by using CREATE TYPE xyz_setting AS ENUM directly on Postgres, and then use that to create your new field as an ENUM (a postgres enum)

Unfortunately, this approach has the downside of breaking the db/schema.rb file.

I think the problem is that the native Postgres types are not supported by the Rails core.

I can reproduce the behavior on Rails 5.17, 5.2.2.4, and 6.0.3

if I do...

class AddXyzToUsers < ActiveRecord::Migration[5.2]
  def up
    execute <<-DDL
          CREATE TYPE xyz_setting AS ENUM (
            'apple', 'bananna', 'cherry'
          );
    DDL
    add_column :users, :xyz, :xyz_setting
  end

  def down
    remove_column  :users, :xyz
    execute "DROP type xyz_setting;"
  end
end

then my schema file is messed up, specifically, the schema users table doesn't get output whatseover, and instead in its place is this message

Could not dump table "users" because of following StandardError

Unknown type 'xyz_setting' for column 'xyz'

Did you try setting config.active_record.schema_format = :sql in the environment configuration files? — Diego Castillo
I wondering if this gives error why its on rails official documentation? ` — buncis
consider to just use normal string since rails enum now support hash/string mapping api.rubyonrails.org/classes/ActiveRecord/Enum.html — buncis

Crysicia Crysicia · Accepted Answer · 2020-11-04T08:23:37

Rails doesn't support custom PG types out of the box.

As stated by Diego Castillo you can use a sql schema which will handle those types.

However, if you want to keep using a ruby schema there's activerecord-postgres_enum, a gem that provides support for PostgreSQL enum data types.

When using Postgres Enum types with Rails, specifying CREATE TYPE xyz_setting AS ENUM in your migration breaks your db/schema.rb file

Could not dump table "users" because of following StandardError

Unknown type 'xyz_setting' for column 'xyz'

2 Answers