优化试卷的删除慢

app/models/exercise_question.rb

@@ -5,11 +5,11 @@ class ExerciseQuestion < ApplicationRecord
   belongs_to :shixun,  optional: true
 
   has_many :exercise_choices, :dependent => :destroy
-  has_many :exercise_answers, :dependent => :destroy
+  has_many :exercise_answers
   has_many :exercise_shixun_challenges,:dependent => :destroy
-  has_many :exercise_shixun_answers, :dependent => :destroy
+  has_many :exercise_shixun_answers
-  has_many :exercise_answer_comments, :dependent => :destroy
+  has_many :exercise_answer_comments
-  has_many :exercise_standard_answers, :dependent => :destroy
+  has_many :exercise_standard_answers
 
   scope :insert_question_ex, lambda {|k| where("question_number > ?",k)}
   scope :find_by_custom, lambda {|k,v| where("#{k} = ?",v)}  #根据传入的参数查找问题