ガントチャート画面表示時のN+1問題解消

lib/redmine/helpers/gantt.rb

@@ -153,7 +153,8 @@ def selected_column_content(options={})
       def issues
         @issues ||= @query.issues(
           :order => ["#{Project.table_name}.lft ASC", "#{Issue.table_name}.id ASC"],
-          :limit => @max_rows
+          :limit => @max_rows,
+          :include => [:children],
         )
       end
 

lib/redmine/nested_set/traversing.rb

@@ -24,6 +24,8 @@ def self.included(base)
         base.class_eval do
           scope :roots, lambda {where :parent_id => nil}
           scope :leaves, lambda {where "#{table_name}.rgt - #{table_name}.lft = ?", 1}
+
+          has_many :children, -> { order(:lft) }, class_name: self.class_name, foreign_key: 'parent_id'
         end
       end
 
@@ -47,15 +49,6 @@ def root
         self_and_ancestors.first
       end
 
-      # Returns the children
-      def children
-        if id.nil?
-          nested_set_scope.none
-        else
-          self.class.order(:lft).where(:parent_id => id)
-        end
-      end
-
       # Returns the descendants that have no children
       def leaves
         descendants.where("#{self.class.table_name}.rgt - #{self.class.table_name}.lft = ?", 1)