Polymorphic lookup - collection

something_lookup.rb

class SomethingLookup < ApplicationRecord
  self.table_name = 'something_lookups'

  belongs_to :something, polymorphic: true

  def self.load_schema!
    # rubocop:disable Naming/MemoizedInstanceVariableName
    @columns_hash ||= {}
    # rubocop:enable Naming/MemoizedInstanceVariableName
  end

  def self.default_scope
    from(default_from)
  end

  def inspect
    inspection = attributes.map { |name, value| "#{name}: #{value}" }.compact.join(', ')
    "#<#{self.class} #{inspection}>"
  end

  def readonly?
    true
  end

   def self.default_from
    <<~SQL
      (
        SELECT concat('a_', id) as id, 'A' as something_type, id as something_id, created_at, updated_at
        FROM as
        UNION ALL
        SELECT concat('b_', id) as id, 'B' as something_type, id as something_id, created_at, updated_at
        FROM bs
      ) #{table_name}
    SQL
  end
end