Reset counter cache on all data of model
To update all the counter cache in one request I found inspiration on http://ryan.mcgeary.org/2016/02/05/proper-counter-cache-migrations-in-rails/
It can be done in one request with SQL :
ActiveRecord::Base.connection.execute <<-SQL.squish
UPDATE games
SET game_participations_count = (SELECT count(1)
FROM game_participations
WHERE game_participations.game_id = games.id)
SQL
It takes much less time to execute since all the updating is done in one request.