Rails application view record for using pure sql files as source of base query for the model

application_view_record.rb

# AUTHOR: Andrei Makarov (github.com/amkisko)

class ApplicationViewRecord < ApplicationRecord
  self.abstract_class = true

  def self.attribute_names
    @attribute_names ||= attribute_types.keys
  end

  def self.load_schema!
    @columns_hash ||= {}

    attributes_to_define_after_schema_loads.each do |name, (cast_type, default)|
      cast_type = cast_type[type_for_attribute(name)] if Proc === cast_type
      cast_type = connection.lookup_cast_type_from_column(type) if Symbol ===
        cast_type
      define_attribute(name, cast_type, default: default)
      @columns_hash[name.to_s] = ActiveRecord::ConnectionAdapters::Column.new(
        name.to_s,
        default
      )
    end
  end

  def self.default_scope
    from("(#{view_definition.gsub(/\s+/, " ").strip}) as #{table_name}")
  end

  def self.view_name
    name.underscore.pluralize
  end

  def self.view_definition_path
    Rails.root.join("db/views", "#{view_name}.sql")
  end

  def self.view_definition
    File.read(view_definition_path)
  end

  def persisted?
    true
  end

  def readonly?
    true
  end
end

db\views\sample_entries.sql

select id as entry_id,
  'FirstEntry' as entry_type,
  some_created_at as created_at,
  some_updated_at as updated_at
from first_entries
union
select id as entry_id,
  'SecondEntry' as entry_type,
  other_created_at as created_at,
  other_updated_at as updated_at
from second_entries

sample_entry.rb

# AUTHOR: Andrei Makarov (github.com/amkisko)

class SampleEntry < ApplicationViewRecord
  belongs_to :entry, polymorphic: true

  attribute :entry_id, :string, default: nil
  attribute :entry_type, :string, default: nil

  attribute :created_at, :datetime, default: nil
  attribute :updated_at, :datetime, default: nil
end