Merge branch 'feature/batch_delete_notification_statistic_data' into 'master'

删除rake 任务

See merge request !9

lib/tasks/data_migrations/version_v1.rake

+namespace :data_migrations do
+  namespace :version do
+  
+    desc "batch delete notification_statistics data"
+    task :v1_batch_delete_notification_statistics_data => :environment do
+      last_object = NotificationStatistic.where("notification_statistics.created_at >= ?", '2020-05-30 16:00:00').first
+
+      puts "rake begin time is #{Time.now.to_s}"
+      NotificationStatistic.in_batches(of: 10000, finish: last_object ) {|records| records.delete_all} if last_object.present?
+      puts "rake end time is #{Time.now.to_s}"
+    end
+  end
+end
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