ADD 定时任务：每晚更新课堂的试卷数量(courses表中的exercises_count字段)

lib/tasks/daily_update_counter_cache_data.rake

@@ -0,0 +1,23 @@
+#coding=utf-8
+# 通过配置服务器的crontab每天定时头歌平台中之前设置的counter_cache数
+# 取消model层面设置的counter_cache回调，解决并发场景下锁表锁行的问题
+namespace :daily_update_counter_cache_data do
+  desc "update counter_cache every day  "
+  task :execute => :environment do
+  	# 更课堂中exercises_count字段
+  	courses = Course.joins(:exercises).select("courses.id, COUNT(exercises.id) AS query_exercises_count").group("courses.id").order("query_exercises_count DESC")
+  	courses = courses.where(id: ENV['update_id']) if ENV['update_id'].present?
+
+  	courses.find_in_batches(batch_size: 10000) do |group|
+  		update_sql = "UPDATE courses SET exercises_count = CASE id "
+  		Parallel.each(group, in_threads: 6) do |course|
+        update_sql += " WHEN #{course.id} THEN  #{course.query_myshixuns_count&.to_i} "
+  		end
+
+      update_sql += " ELSE exercises_count END WHERE id IN (#{group.map(&:id).join(',')})"
+      Rails.logger.info "########## #{Time.now} 更新课堂exercises_count的SQL语句: #{update_sql}"
+      ActiveRecord::Base.connection.execute(update_sql) if group.present?
+  	end
+  	
+  end
+end