message unique open rate

message.rb

def unique_open_rate
    recipient_activities = recipient_messages.joins(:activities)
    ((recipient_activities.where("activities.activity_type = 'open'").distinct.count.to_f / recicipient_messages.count) * 100).round(2)
end

query 

user.messages.select("messages.*,
            COUNT(DISTINCT recicipient_messages.id) recipient_count,
            COUNT(DISTINCT activities.id) total_activities,
            COUNT(CASE WHEN activities.activity_type = 0 THEN 1 ELSE null END) as unique_opens,
            COUNT(CASE WHEN activities.activity_type = 1 THEN 1 ELSE null END) as unique_views,
            COUNT(CASE WHEN activities.activity_type = 2 THEN 1 ELSE null END) as unique_responses")
          .joins(:video, recicipient_messages: :activities)
          .group("messages.id")