Laravel - 渴望加载多态关系的相关模型 [英] Laravel - Eager Loading Polymorphic Relation's Related Models

问题描述

我可以急切地加载多态关系/模型，而不会出现任何 n+1 问题.但是，如果我尝试访问与多态模型相关的模型，则会出现 n+1 问题，我似乎无法找到解决方法.这是在本地查看的确切设置:

I can eager load polymorphic relations/models without any n+1 issues. However, if I try to access a model related to the polymorphic model, the n+1 problem appears and I can't seem to find a fix. Here is the exact setup to see it locally:

1) 数据库表名/数据

历史

公司

产品

服务

2) 模型

// History
class History extends Eloquent {
    protected $table = 'history';

    public function historable(){
        return $this->morphTo();
    }
}

// Company
class Company extends Eloquent {
    protected $table = 'companies';

    // each company has many products
    public function products() {
        return $this->hasMany('Product');
    }

    // each company has many services
    public function services() {
        return $this->hasMany('Service');
    }
}

// Product
class Product extends Eloquent {
    // each product belongs to a company
    public function company() {
        return $this->belongsTo('Company');
    }

    public function history() {
        return $this->morphMany('History', 'historable');
    }
}

// Service
class Service extends Eloquent {
    // each service belongs to a company
    public function company() {
        return $this->belongsTo('Company');
    }

    public function history() {
        return $this->morphMany('History', 'historable');
    }
}

3) 路由

Route::get('/history', function(){
    $histories = History::with('historable')->get();
    return View::make('historyTemplate', compact('histories'));
});

4) 仅因为 $history->historable->company->name 而记录了 n+1 的模板，将其注释掉，n+1 消失.. 但我们需要那个遥远相关的公司名称:

@foreach($histories as $history)
    <p>
        <u>{{ $history->historable->company->name }}</u>
        {{ $history->historable->name }}: {{ $history->historable->status }}
    </p>
@endforeach
{{ dd(DB::getQueryLog()); }}

我需要能够急切地(在单个查询中)加载公司名称，因为它是多态关系模型 Product 和 Service 的相关模型.我已经为此工作了几天，但找不到解决方案.History::with('historable.company')->get() 只是忽略 historable.company 中的 company.这个问题的有效解决方案是什么?

I need to be able to load the company names eagerly (in a single query) as it's a related model of the polymorphic relation models Product and Service. I’ve been working on this for days but can't find a solution. History::with('historable.company')->get() just ignores the company in historable.company. What would an efficient solution to this problem be?

推荐答案

解决方案:

有可能，如果你添加:

protected $with = ['company']; 

同时适用于 Service 和 Product 模型.这样，每次加载 Service 或 Product 时，都会预先加载 company 关系，包括通过与 <代码>历史.

to both the Service and Product models. That way, the company relation is eager-loaded every time a Service or a Product is loaded, including when loaded via the polymorphic relation with History.

说明:

这将导致另外 2 个查询，一个针对 Service，一个针对 Product，即每个 historable_type 一个查询.所以你的查询总数——不管结果 n 的数量——来自 m+1 (没有急切加载遥远的 company 关系) 到 (m*2)+1，其中 m 是由多态关系链接的模型数.

This will result in an additional 2 queries, one for Service and one for Product, i.e. one query for each historable_type. So your total number of queries—regardless of the number of results n—goes from m+1 (without eager-loading the distant company relation) to (m*2)+1, where m is the number of models linked by your polymorphic relation.

可选:

这种方法的缺点是您将总是在 Service 和 Productcompany 关系代码>模型.这可能是也可能不是问题，具体取决于您的数据的性质.如果这是一个问题，您可以使用此技巧在调用多态关系时自动预先加载 company only.

The downside of this approach is that you will always eager-load the company relation on the Service and Product models. This may or may not be an issue, depending on the nature of your data. If this is a problem, you could use this trick to automatically eager-load company only when calling the polymorphic relation.

将此添加到您的 History 模型中:

Add this to your History model:

public function getHistorableTypeAttribute($value)
{
    if (is_null($value)) return ($value); 
    return ($value.'WithCompany');
}

现在，当您加载 historable 多态关系时，Eloquent 将查找类 ServiceWithCompany 和 ProductWithCompany，而不是 Service 或 产品.然后，创建这些类，并在其中设置 with:

Now, when you load the historable polymorphic relation, Eloquent will look for the classes ServiceWithCompany and ProductWithCompany, rather than Service or Product. Then, create those classes, and set with inside them:

ProductWithCompany.php

class ProductWithCompany extends Product {
    protected $table = 'products';
    protected $with = ['company'];
}

ServiceWithCompany.php

class ServiceWithCompany extends Service {
    protected $table = 'services';
    protected $with = ['company'];
}

...最后，您可以从基础 Service 和 Product 类中删除 protected $with = ['company'];.

...and finally, you can remove protected $with = ['company']; from the base Service and Product classes.

有点hacky，但它应该可以工作.

A bit hacky, but it should work.

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