Question

我的控制器中有以下代码：

@unanswered_questions = Question.unanswered_with_tag(params[:tag_id]).paginate(per_page: 10, page: params[:page])

在我的Question模型中调用此方法：

def self.unanswered_with_tag id
  joins(:taggings).where(taggings: { tag_id: id }).where(questions: { num_answers: 0})
end

我希望有一个sql查询可以获取该页面上的前10个未答复的问题，但我的日志显示了2个查询：

 Question Load (0.4ms)  SELECT  "questions".* FROM "questions"  
 INNER JOIN "taggings" ON "taggings"."question_id" = "questions"."id" 
 WHERE "taggings"."tag_id" = $1 AND "questions"."num_answers" = $2 
 ORDER BY "questions"."id" ASC LIMIT $3 OFFSET $4  
 [["tag_id", 3], ["num_answers", 0], ["LIMIT", 1], ["OFFSET", 0]]

^^注意LIMIT 1部分。

第二个问题：

 SELECT  "questions".* FROM "questions" INNER JOIN "taggings"  
   ON "taggings"."question_id" = "questions"."id" 
   WHERE "taggings"."tag_id" = $1 AND "questions"."num_answers" = $2 
   LIMIT $3 OFFSET $4  
   [["tag_id", 3], ["num_answers", 0], ["LIMIT", 10], ["OFFSET", 0]]

哪个有限制10.

为什么会出现这种情况？

Answer 1

您是否在视图中运行代码，检查@unanswered_questions是否有任何行（例如#exists？）以显示值？

为什么我的代码会产生额外的查询？

1 个答案: