通过预先加载关联记录,可以避免 N+1 查询问题,即对每条关联记录执行额外查询。下面是一个N+1查询问题的示例,然后我们将介绍一种名为俄罗斯娃娃缓存(Russian Doll Caching)的替代技术。 # N+1 query problem users = User.all users.each{|user| puts user.posts.count}# Executes one query for users and N ...
Efficient SQL queries and Rails’ optimization features help prevent common performance issues like the ‘N+1 query’ problem. Migrations and Schema Management Database migrations allow you to version control your database schema, enabling developers to modify tables and columns over time while tracking...
One of the most common performance issues is the N+1 query problem. This issue occurs when an application makes multiple requests to a database for data that could have been retrieved in one request. To improve your Ruby on Rails app performance, it’s important to solve this problem by o...
Prosopite monitors all SQL queries using the Active Support instrumentation and looks for the following pattern which is present in all N+1 query cases: More than one queries have the same call stack and the same query fingerprint. Installation Add this line to your application's Gemfile: gem...
Much more efficient. This solution to the N+1 query problem is an example of the kind of inefficiencies that we might find if we peered under the hood of an application in which the developer hadn’t been attentive to the log files. ...
1、求和公式及性质 前n项和 a1+a2+a3+a4+…+an用下面方式表示 初中学过前n项和公式 n(n+1)/2.即 首相1加末相n,乘n除二. 无限数列a1+a2+a3+…记做 极限形式 说明: 当此极限存在时称为收敛,不存在时称为发散.当|ak|(表示取绝...shell中awk的基础知识 shell脚本——awk文本和数据处理编程语言...
N+1 Queries is a serious database performance problem. Be careful of that situation! If you're not sure, I recommend you install http://github.com/flyerhzm/bullet plugin, which helps you reduce the number of queries with alerts (and growl). Read More Tags model plugin Use Observer ...
So what’s the problem. Check details. Check brakeman help for further information about the option. 1 2 3 ➜ design_studio git:(feature/github-ci) brakeman --help | grep warn -z, --[no-]exit-on-warn Exit code is non-zero if warnings found (Default) --ensure-ignore-notes Fail...
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Usually, your query will look something like this: SELECT users.* FROM users WHERE NOT EXISTS (SELECT 1 FROM stepper_motor_journeys WHERE type = 'YourJourney' AND hero_id = users.id) To make this simpler, we offer a special helper method: YourJourney.presence_sql_for(User) # => ...