temp.rb

class UserIdentity
  def cas_attachments
    sql = id_column.in(cas_attachment_belongs_to_my_cas).or(id_column.in(cas_attachment_belongs_to_my_programs))

    CasAttachment.where(sql)
  end

  def table
    CasAttachment.arel_table
  end

  def cas_attachment_belongs_to_my_cas
    CasAttachment.for_cas(cas).select(:id).ast
  end

  def cas_attachment_belongs_to_my_programs
    CasAttachment.for_program(programs.select(:id)).select(:id).ast
  end

  def id_column
    table[:id]
  end
end