diff --git a/app/models/message.rb b/app/models/message.rb
index 26946f6d0..d3d507a72 100644
--- a/app/models/message.rb
+++ b/app/models/message.rb
@@ -56,11 +56,10 @@ class Message < ApplicationRecord
     from_board = Board.find(messages.first.board_id)
 
     root_ids = messages.map(&:id)
-    children = Message.where(parent_id: root_ids).select(:id).to_a
-    children_ids = children.map(&:id)
-    second_children = Message.where(parent_id: children_ids).select(:id).to_a
+    children_ids = Message.where(parent_id: root_ids).pluck(:id)
+    second_children_ids = Message.where(parent_id: children_ids).pluck(:id)
 
-    ids = root_ids.concat(children_ids).concat(second_children.map(&:id)).uniq
+    ids = root_ids.concat(children_ids).concat(second_children_ids).uniq
 
     ActiveRecord::Base.transaction do
       Message.where(id: ids, board_id: from_board.id).update_all(board_id: to_board.id)
diff --git a/lib/tasks/course_board_message_count.rake b/lib/tasks/course_board_message_count.rake
new file mode 100644
index 000000000..d1ac5524d
--- /dev/null
+++ b/lib/tasks/course_board_message_count.rake
@@ -0,0 +1,24 @@
+namespace :course_board do
+  desc 'transfer children message to root message board'
+  task children_message_transfer: :environment do
+    Board.find_each do |board|
+      logger("Current transfer board id: #{board.id} ~")
+
+      root_subquery = board.messages.where(parent_id: nil).reorder(nil).pluck(:id)
+      next if root_subquery.blank?
+      children_subquery = Message.where(parent_id: root_subquery).reorder(nil).pluck(:id)
+      next if children_subquery.blank?
+      second_children_subquery = Message.where(parent_id: children_subquery).reorder(nil).pluck(:id)
+
+      ids = children_subquery.concat(second_children_subquery).uniq
+      Message.where(id: ids).update_all(board_id: board.id)
+
+      Board.reset_counters(board.id, :messages)
+      logger("transfer success ~")
+    end
+  end
+
+  def logger(msg)
+    puts msg
+  end
+end
\ No newline at end of file