activerecord | 易学教程

Unable to use TimescaleDB in Rails test environment

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问题 I'm stuck using TimescaleDB in Rails - everything works fine in development, but in my test suite I cannot insert any data. What I tried A) Use SQL schema dump This causes the original error message I saw. It does create parts of the schema for TimescaleDB but not all of it. I have a hypertable but it's not working properly B) Use Ruby schema dump This lets me insert into my table but it's not a hypertable at all - the ruby syntax looses everything related to TimescaleDB and hypertables. C)

ActiveRecord model.update_column with subquery

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问题 I want to update a column in a Supply model that updates with its stock based on a sum of a subset. The thing is that actually hits two queries to make it works. total_stock = History.sum(:quantity) # first query Supply.update_columns(stock: total_stock) # second query Then, I tried to write a subquery so: total_stock_subquery = mysubset.select(Arel.sql('SUM(quantity)')).to_sql Supply.update_columns(stock: total_stock_subquery) # it should be only one query But, ActiveRecord will replace the

Complex nested aggregations to get order totals - part 2

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问题 Follow-up to this answered question: Complex nested aggregations to get order totals After getting it answered I realized that it would be much easier if I start of with: Budget.find(2).cbs_items.order('cbs_items.name ASC').select(:id, :name) Budget Load (0.3ms) SELECT "budgets".* FROM "budgets" WHERE "budgets"."company_id" = 9 AND "budgets"."id" = $1 LIMIT $2 [["id", 2], ["LIMIT", 1]] CbsItem Load (1.6ms) SELECT "cbs_items"."id", "cbs_items"."name" FROM "cbs_items" INNER JOIN "cost_breakdown

Do Heroku staging apps share database with review apps?

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问题 I've noticed some odd behaviour when working with review apps. I created a review app for a pull request I was working on. It's parent was my staging app. As part of the pull request I migrated the database many times and I was testing those migrations with the review app. I'm working with Rails. I was preparing to merge my changes and deploy to the staging app, but I noticed that the data in my staging app had changed. There have been no deploys to staging since I started this work. For

Do Heroku staging apps share database with review apps?

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Override the default Rails model template

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问题 I want to override the default model file that's generated with rails generate model . I've created a template based on this file, but I can't figure out where to put it. Other answers seem to suggest /lib/templates/rails/model/model.rb or /lib/templates/rails/model/model_generator.rb , but neither of those do anything - I put the template in that location but when I run rails generate model ModelName it gets ignored. Am I going about this the right way? Where should I put the template? 回答1:

Enabling the hstore extension in Amazon RDS from Rails 4

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问题 I have a Rails 4 application that uses ActiveRecord to interact with a PostgreSQL 9.3 database. The application makes use of the hstore extension in PostgreSQL for storing key-value pairs in a single database field. Accordingly, Rails automatically detects what I did with that migration and creates the following line in your schema.rb file enable_extension "hstore" In the development and test environments, that works great, as I am deploying to stand-alone PostgreSQL instances. However in

Rails - Active Record: add extra select column to find(:all)

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问题 I want to add new column sum(time_entries.hours) to sql select I'm querying entries like this: issues = Issue.visible.where(options[:conditions]).all( :include => ([:status, :project, :time_entries] + (options[:include] || [])).uniq, :conditions => statement, :order => order_option, :joins => query_joins(order_option.join(',')), :limit => options[:limit], :offset => options[:offset], :group => "#{Issue.table_name}.id" ) It generates this select: SELECT "issues"."id" AS t0_r0, ... "time

YII2组件之GridView

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采用的是yii2.0.14版本，为了学习方便，以问答式书写。开始GridView GridView主要是为了实现表格复用，尤其我们做后台的时候，你发现表单和表格占据了大部分页面，而表格的样式又是高度的统一，那么如果有这样一个挂件，传入数据集自动渲染表格该多好。于是GridView出现了，一个有细节、够稳定的表格渲染挂件。通常情况下GridView是和各种dataProvider配合使用，针对于yii2框架中的dataProvider我之前写过一篇文章，你可以看下，这将有助于你对GridView的学习。在学习GridView挂件之前，我们需要先了解GridView的结构，看下图。简单的说，一个GridView由N个column（列）组成，而每个列里有自己的header、content和footer操作，这在GridView的代码中有所体现 try { echo GridView:: widget([ 'dataProvider' => $dataProvider , 'columns'=> [ 'id', 'created_at:datetime:生成时间', [ 'label'=>'会员名', 'attribute'=>'username', 'format'=>'text' ] , ] ]); } catch (\ Exception $e ){ // todo }

小记----Mybatis

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使用mybatis操作数据库有两种方式xml注入和@注解方式，两种方式在项目中是可以共存的。注解方式：使用注解方式默认需要实体类的属性值和表的列名保持一致，否则无法映射到对应的值；或者使用@Results来手动设置映射关系，优点：看着优雅一点，方便修改，缺点：动态sql语句不好写，比较麻烦 xml形式：很常用的方式，有各种逆向工程可以生成mapper.xml文件，看着比较乱，各种标签满天飞，修改的时候很痛苦我们会发现无论是hibernate还是mybatis，为了方便我们的写sql都煞费苦心。但最后他们都殊途同归指向了“约定大于配置”。hibernate搞了个jpa，而mybatis也相应推出了mp。而mp 是一个 MyBatis 的增强工具。看看官网对他的介绍：无侵入：只做增强不做改变，引入它不会对现有工程产生影响，如丝般顺滑损耗小：启动即会自动注入基本 CURD，性能基本无损耗，直接面向对象操作强大的 CRUD 操作：内置通用 Mapper、通用 Service，仅仅通过少量配置即可实现单表大部分 CRUD 操作，更有强大的条件构造器，满足各类使用需求支持 Lambda 形式调用：通过 Lambda 表达式，方便的编写各类查询条件，无需再担心字段写错支持主键自动生成：支持多达 4 种主键策略（内含分布式唯一 ID 生成器 - Sequence）