Polymorphic Joins

model.rb

# frozen_string_literal: true

class Model < ApplicationRecord
  extend PolymorphicJoins

  belongs_to :profile, polymorphic: true # can be Client::Profile or Freelancer::Profile models
  
  scope :clients, -> { polymorphic_joins(Client::Profile) }
end

polymorphic_joins.rb

# frozen_string_literal: true

module PolymorphicJoins
  def polymorphic_joins(model, prefix: find_prefix, join_type: 'INNER')
    target_table = model.table_name
    sql = <<~SQL.squish
      #{join_type} JOIN #{target_table}
      ON #{target_table}.id = #{table_name}.#{prefix}_id
    SQL
    joins(sql).where("#{prefix}_type": model.to_s)
  end

  private

  def find_prefix
    prefix = column_names.find { |col| col.ends_with?('_type') }
    &.delete_suffix('_type')

    unless prefix && column_names.find { |col| col == "#{prefix}_id" }
      raise NoPolymorphismError, "#{name} doesn't have any polymorphic associations"
    end

    prefix
  end

  class NoPolymorphismError < StandardError; end
end

there's a better way, see other gist : https://gist.github.com/mpressen/73e0b8dd40be7775a45f88ec72cf6674