schema.rb crashes for enum type in postgres

Question

I am using gender field of my user table as enum type.

Migration also runs sucessfully. But the schema.rb get crashes.

After running the migration, my schema.rb looks:

ActiveRecord::Schema.define(version: 2018_07_23_115046) do

    # These are extensions that must be enabled in order to support this database
    enable_extension "plpgsql"

    # Could not dump table "users" because of following StandardError
    # Unknown type 'gender' for column 'gender'

end

my migration is:

class AddGenderToUsers < ActiveRecord::Migration[5.2]
  def up
    execute <<-SQL
      CREATE TYPE gender AS ENUM ('male', 'female', 'not_sure', 'prefer_not_to_disclose');
    SQL

    add_column :users, :gender, :gender, index: true
  end

  def down
    remove_column :users, :gender

    execute <<-SQL
      DROP TYPE gender;
    SQL
  end
end

I don't understand why the schema.rb crashes.

Answer 1

Custom enum types in PostgreSQL (Rails 7+)

schema.rb is crashing since Rails had no built-in support for custom enum types in PostgreSQL.

Starting from Rails 7, a new create_enum method is introduced that allows to write migrations like so:

# db/migrate/20131220144913_create_articles.rb
def up
  create_enum :article_status, ["draft", "published"]

  create_table :articles do |t|
    t.enum :status, enum_type: :article_status, default: "draft", null: false
  end
end

# There's no built in support for dropping enums, but you can do it manually.
# You should first drop any table that depends on them.
def down
  drop_table :articles

  execute <<-SQL
    DROP TYPE article_status;
  SQL
end

This way schema.rb will be updated automatically and there is no need to change config.active_record.schema_format to sql (at least for this particular case).

Sources:

• Pull Request.
• Rails Guides.
• Rails API.
• Rails 7 adds better support for custom enum types in PostgreSQL by Saeloun.