eager-loading

问题 I need to alias when I do a Laravel eager loading: $posts = Post::with(array('images as main_image' => function($query) // do not run { $query->where('number', '=', '0'); })) ->where('id', '=', $id) ->get(); return Response::json($posts); I need to to this because I want the JSON response like this: [ { "id": 126, "slug": "abc", "name": "abc", "created_at": "2014-08-08 08:11:25", "updated_at": "2014-08-28 11:45:07", "**main_image**": [ { "id": 223, "post_id": 126 ... } ] } ] It is possible?

问题 I am having trouble with the Dagger 2 dependency injection framework. I would like to create an EagerSingleton . I assume that dagger 2 creates lazy loaded singletons when I use the @Singleton annotation. How do I create EagerSingleton using the Dagger 2 framework ? 回答1: I solved this by creating an EagerModule which had a single provide method which returned Void . Everything I wanted created eagerly I specified as parameters to that method. Then I added a Void init() method to the Component

问题 My confusion stems from this question, where OP has a model like class Quote < ActiveRecord::Base has_many :items def calc_price sum = 0 #logic for summation end end In the answers, a couple of people have suggested using the sum method directly for calculating the sum of attributes def total_price items.sum('price') end If I eager load data using Quote.includes(:items).find(:all) , does the sum happen at the database's end, or does it use the objects already loaded in memory? If it uses the

问题 I got two DB tables: Posts $table->increments('id'); $table->integer('country_id')->unsigned(); $table->foreign('country_id')->references('id')->on('countries'); Countries $table->increments('id'); $table->string('name', 70); I use laravel as back-end. Now I want to implement filtering data for my front-end. So the user can select a country name and laravel should answer the request only with posts that have a country with the specified name. How could I add this condition to my existing

问题 I'm using EF Code First and I have a navigation property called Category that I want eager loaded in every call: public class Product { ... public Category Category { get; set; } } To do this I have to include it in every call I'll do on Product var results = from p in db.Products.Include("Category") select p; Is there a way to have Category property eager loaded, therefore generation a SQL join, in every call without having to include it every time? thank you 回答1: You can use helper method

问题 1) How can use eager loading here, i mean just by using $SponceringUser instead of $ProfileUser. so i don't need to run two separate queries. if i exchange my $profileUser variable with $SponceringUser where in the code i should save it to get the right output here is the Post_edit method for more details please refer gist here : https://gist.github.com/gupta2205/b33dcf762876e5df34d9 public function post_edit($id = null) { if ($id) { $Petition = Petition::find($id); if (!$Petition) { //oh

问题 In the last days i'm making a sample application to apply/study DDD. One of the principles of DDD(Please correct me if I'm wrong) is that all the changes to an entity should be made through the Aggregate Root(AR) and an AR should be loaded with his child entities. In this way is eaiser to validate Aggregate consistency. There is only a little big detail that is bothering me. I'm not able to understand how DDD is dealing with performance issues. Imagine that i have an Order(AR) that have, let

问题 I'm running an into issue where Sequelize creates a subquery of the primary model and then joins the includes with that subquery instead of directly with the primary model table. The query conditions for the include(s) ends up inside the subquery's WHERE clause which makes it invalid. I have shortened names down trying to keep this compact hopefully without losing any relevant info. Environment: Nodejs: 6.11.3 Sequelize: 3.23.6 => Updated to 4.38.1 and problem persists MySql: 5.7.23 Code snip

问题 I'm trying to optimize some of our queries. One particular challenge was trying to eager load a polymorphic model. In this case, UserView is polymorphic and has the following columns: user_id, user_viewable_id, user_viewable_type When I try to run this query. @user_views = UserView.select('user_views.* AS user_views, songs.* AS songs, users.* AS users') .joins('INNER JOIN users AS users ON user_views.user_id = users.id') .joins('INNER JOIN songs AS songs ON user_views.user_viewable_id = songs

问题 Let's say I want to display a list of books and their authors. In traditional database design, I would issue a single query to retrieve rows from the Book table as well as the related Author table, a step known as eager fetching . This is done to avoid the dreaded N+1 select problem : If the Author records were retrieved lazily, my program would have to issue a separate query for each author, possibly as many queries as there are books in the list. Does Google App Engine Datastore provide a