What's The Impact of Eager_Load=True

What's the impact of eager_load=true?

However this raises some questions like how does a test run without loading Rails and application related code?

The test loads the necessary code on demand as it tries to use it.
So for example on some code line the test wants to use the ActiveRecord class. With eager_load set to false this class is not required yet, which will lead to an exception on a vanilla ruby program. Within a rails project however the test will require ActiveRecord on demand as it uses it. So at the end a single test runs faster, because only the code parts it needed have been required.

This technique is the opposite of eager loading and it's called autoloading

What is the Rails and application related code that is being eager loaded?

Check out https://github.com/rails/rails. It's a bunch of stuff.

Are all of these classes and their subclasses being eager loaded?

yes

What are the clear disadvantages of using eager_load = false in development or testing environment?

In development environment it's an advantage and a best practice as you get faster boot times (neglected when using a preloader like spring). Probably it's also easier for reloading changes along with the cache_classes=false option, as you have less to reload (just an assumption).

In test environment sometimes you just can't use eager_load=false if you want to estimate some code metrics
like code coverage or doing style checks. E.g. simple_cov requires you to eager load all the code before starting tests.

And in general it can happen that some library can't be used with eager loading because it does some initialization on loading a class which has to be already available even before calling its methods. However this is a rare case, having said that, it happened to us with the neo4j.rb gem

What's the performance impact of disabling eager_load in production.rb?

Setting eager_load=false will probably speed up your app's startup, because loading will be deferred until necessary.

However, the penalty is that your app will likely use more memory (which is usually the most scarce server resource). I suspect that you may also run into threading bugs if you use a multithreaded server (e.g. puma) with eager_load=false.

Since Rails automatically includes all app/* directories in its eager load paths, I can't think of an easy way to exclude app/models/legacy while eager-loading everything else.

Instead, you could move the contents of app/models/legacy to e.g. legacy/ at the root of your project and add that to the autoload_paths:

config.autoload_paths += %W( #{config.root}/legacy )

Now Rails will still be able to find those files, but they won't be eagerly loaded in production.

Rails 5: rails s production with config.eager_load=true fails while gem 'gem_name', require: false

I researched for a bit, try upating bootsnap gem, try delete 'bootsnap-load-path-cache' and 'bootsnap-compile-cache' from tmp/cache folder.
This article May help understand eager load https://blog.arkency.com/2014/11/dont-forget-about-eager-load-when-extending-autoload/

This topic may help understand
What's the impact of eager_load=true?

it points to other solution, not require but autoload(http://www.rubyinside.com/ruby-techniques-revealed-autoload-1652.html)

From the guides(please read):
https://guides.rubyonrails.org/autoloading_and_reloading_constants.html#autoload-paths-and-eager-load-paths

Meaning of using 'eager:true' option in TypeORM

As explained in the Eager Loading Documentaion You can set the eager: true on one side of the relationship only. That means you have define the relationship like below.

in User.ts

@OneToMany(type => Post, post => post.user, { eager: true })
posts: Post[]

and in Post.ts

@ManyToOne(type => User, user => user.posts)
user: User

And in here if you use await User.findOne({ uid: ctx.uid }) in functions that will load Post relationship automatically. This does not mean you cannot use the vice versa relationship. From Post to User relationship you can load the relationship still using leftJoinAndSelect.

ActiveRecord: Loading records with all child association eager loaded, but select the ones that any of the children hits the condition

Hey you can achieve this using ActiveRecord's query as

@unfinished = Assignment.where(:finished => false).pluck(:project_id)

@projects = Project.includes(:assignments).where(:id => @unfinished)

Active Record with sql in single query as,

 Project.includes(:assignments).where("projects.id in (select project_id from assignments where assignments.finished = ?)", false)

config.assets.compile = false - makes heroku not display my images in production

Setting the value to true will compile the assets for each request. When set to false , you need to ensure your assets are already precompiled.

You can do so by running the following command before starting your server in production mode:

RAILS_ENV=production rake assets:clobber
RAILS_ENV=production rake assets:precompile

clobber will remove the precompiled assets from the public directory and precompile will compile the assets and store them in the public directory.

Hope this helped.

Laravel / Eloquent eager loading

You should define the method in your model. As far as I see you're going to have one to many relationship. And that's going to be

class Question extends Model
{
    public function tags()
    {
        return $this->hasMany('App\Tag');
    }
}

Tag class

class Tag extends Model
{
    public function question()
    {
        return $this->belongsTo('App\Question');
    }
}

And the controller. Instead of all() use get() method.

$questions = Question::with('tags')->get();

As I defined tags method in the Question model. Question::with('tags') should call it. Instead, if you're going to do Question::with('tag'), tag method should be defined in Question model.

Notice the s

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