zammad/app/jobs/ticket_user_ticket_counter_job.rb

class TicketUserTicketCounterJob < ApplicationJob
  def perform(customer_id, updated_by_id)

    # check if update is needed
    customer = User.lookup(id: customer_id)
    return if !customer

    # count open and closed tickets of customer
    ticket_count = {
      closed: 0,
      open:   0,
    }

    if customer_id != 1
      ticket_count.each_key do |ticket_state_category|
        ticket_states    = Ticket::State.by_category(ticket_state_category)
        ticket_state_ids = ticket_states.map(&:id)
        tickets          = Ticket.where(
          customer_id: customer_id,
          state_id:    ticket_state_ids,
        )
        ticket_count[ticket_state_category] = tickets.count
      end
    end

    needs_update = false
    ticket_count.each_key do |ticket_state_category|
      preferences_key = ('tickets_' + ticket_state_category.to_s).to_sym
      next if customer[:preferences][preferences_key] == ticket_count[ticket_state_category]

      needs_update = true
      customer[:preferences][preferences_key] = ticket_count[ticket_state_category]
    end
    return if !needs_update

    customer.updated_by_id = updated_by_id
    customer.save
  end
end