matchings_by_dates.rb

dates_matchings = {}

Matching.unscoped.select([:id, :created_at]).find_each do |matching|
  dates_matchings[matching.created_at.to_date.to_s] ||= 0
  dates_matchings[matching.created_at.to_date.to_s] += 1
end; nil

dates_matchings.sort.each do |date, matchings_count|
  puts "#{date}\t#{matchings_count}"
end; nil

matchings_by_dates_for_taiwan.rb

dates_matchings = {}

Matching.unscoped.includes(:player).where('matchings.id > 16925949').select([:id, :player_id, :created_at]).find_in_batches do |matchings|
  matchings.select { |m| m.player.service_zone_id == 'taiwan' }.each do |matching|
    dates_matchings[matching.created_at.to_date.to_s] ||= 0
    dates_matchings[matching.created_at.to_date.to_s] += 1
  end
end; nil

dates_matchings.sort.each do |date, matchings_count|
  puts "#{date}\t#{matchings_count}"
end; nil