詳解Laravel之模型關聯預加載

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詳解Laravel之模型關聯預加載

Laravel學習筆記之模型關聯預加載

說明:本文主要說明Laravel Eloquent的延遲預加載(Eager Loading),使用延遲預加載來減少MySQL查詢次數。同時,作者會將開發過程中的一些截圖和代碼黏上去,提高閱讀效率。

備注:現在有4張表:商家表merchants、商家電話表phones、商家擁有的店鋪shops表和店鋪里的商品表products。并且關系是:

[     'merchants_phones' => 'one-to-one',     'merchants_shops'  => 'one-to-many',     'shops_products'   => 'one-to-many', ]

現在要求做出一個頁面以列表形式顯示每個店鋪,每個店鋪塊包含店鋪信息如標題、包含店鋪商家信息如姓名和電話、包含擁有的商品信息如介紹和價格。看看有沒有預加載會有什么不同。

開發環境:Laravel5.1+MAMP+PHP7+MySQL5.5

先寫個店鋪列表頁

1.先裝上開發插件三件套(具體可參考:Laravel學習筆記之Seeder填充數據小技巧)
不管咋樣,先裝上開發插件三件套:

composer require barryvdh/laravel-debugbar --dev composer require barryvdh/laravel-ide-helper --dev composer require mpociot/laravel-test-factory-helper --dev  //config/app.php /**  *Develop Plugin  */         BarryvdhDebugbarServiceProvider::class, MpociotLaravelTestFactoryHelperTestFactoryHelperServiceProvider::class, BarryvdhLaravelIdeHelperIdeHelperServiceProvider::class,

2.寫上表字段、表關聯和測試數據填充器Seeder
依次輸入指令:

php artisan make:model Merchant -m php artisan make:model Phone -m php artisan make:model Shop -m php artisan make:model Product -m

寫上表字段和表關聯:

class CreateMerchantsTable extends Migration {     /**      * Run the migrations.      *      * @return void      */     public function up()     {         Schema::create('merchants', function (Blueprint $table) {             $table->increments('id');             $table->string('username')->unique();             $table->string('email')->unique();             $table->string('first_name');             $table->string('last_name');             $table->timestamps();         });     }      /**      * Reverse the migrations.      *      * @return void      */     public function down()     {         Schema::drop('merchants');     } }  class CreatePhonesTable extends Migration {     /**      * Run the migrations.      *      * @return void      */     public function up()     {         Schema::create('phones', function (Blueprint $table) {             $table->increments('id');             $table->integer('number')->unsigned();             $table->integer('merchant_id')->unsigned();             $table->timestamps();             $table->foreign('merchant_id')                 ->references('id')                 ->on('merchants')                 ->onUpdate('cascade')                 ->onDelete('cascade');         });     }      /**      * Reverse the migrations.      *      * @return void      */     public function down()     {         Schema::table('phones', function($table){             $table->dropForeign('merchant_id'); // Drop foreign key 'user_id' from 'posts' table         });         Schema::drop('phones');     } }  class CreateShopsTable extends Migration {     /**      * Run the migrations.      *      * @return void      */     public function up()     {         Schema::create('shops', function (Blueprint $table) {             $table->increments('id');             $table->string('name');             $table->string('slug')->unique();             $table->string('site');             $table->integer('merchant_id')->unsigned();             $table->timestamps();             $table->foreign('merchant_id')                 ->references('id')                 ->on('merchants')                 ->onUpdate('cascade')                 ->onDelete('cascade');         });     }      /**      * Reverse the migrations.      *      * @return void      */     public function down()     {         Schema::table('shops', function($table){             $table->dropForeign('merchant_id'); // Drop foreign key 'user_id' from 'posts' table         });         Schema::drop('shops');     } }  class CreateProductsTable extends Migration {     /**      * Run the migrations.      *      * @return void      */     public function up()     {         Schema::create('products', function (Blueprint $table) {             $table->increments('id');             $table->string('name');             $table->text('short_desc');             $table->text('long_desc');             $table->double('price');             $table->integer('shop_id')->unsigned();             $table->timestamps();             $table->foreign('shop_id')                 ->references('id')                 ->on('shops')                 ->onUpdate('cascade')                 ->onDelete('cascade');         });     }      /**      * Reverse the migrations.      *      * @return void      */     public function down()     {         Schema::table('products', function($table){             $table->dropForeign('shop_id'); // Drop foreign key 'user_id' from 'posts' table         });         Schema::drop('products');     } }  /**  * AppMerchant  *  * @property integer $id  * @property string $username  * @property string $email  * @property string $first_name  * @property string $last_name  * @property CarbonCarbon $created_at  * @property CarbonCarbon $updated_at  * @property-read AppPhone $phone  * @property-read IlluminateDatabaseEloquentCollection|AppShop[] $shops  * @method static IlluminateDatabaseQueryBuilder|AppMerchant whereId($value)  * @method static IlluminateDatabaseQueryBuilder|AppMerchant whereUsername($value)  * @method static IlluminateDatabaseQueryBuilder|AppMerchant whereEmail($value)  * @method static IlluminateDatabaseQueryBuilder|AppMerchant whereFirstName($value)  * @method static IlluminateDatabaseQueryBuilder|AppMerchant whereLastName($value)  * @method static IlluminateDatabaseQueryBuilder|AppMerchant whereCreatedAt($value)  * @method static IlluminateDatabaseQueryBuilder|AppMerchant whereUpdatedAt($value)  * @mixin Eloquent  */ class Merchant extends Model {     /**      * @return IlluminateDatabaseEloquentRelationsHasOne      */     public function phone()     {         return $this->hasOne(Phone::class, 'merchant_id');     }      /**      * @return IlluminateDatabaseEloquentRelationsHasMany      */     public function shops()     {         return $this->hasMany(Shop::class, 'merchant_id');     } }  /**  * AppPhone  *  * @property integer $id  * @property integer $number  * @property integer $merchant_id  * @property CarbonCarbon $created_at  * @property CarbonCarbon $updated_at  * @property-read AppMerchant $merchant  * @method static IlluminateDatabaseQueryBuilder|AppPhone whereId($value)  * @method static IlluminateDatabaseQueryBuilder|AppPhone whereNumber($value)  * @method static IlluminateDatabaseQueryBuilder|AppPhone whereMerchantId($value)  * @method static IlluminateDatabaseQueryBuilder|AppPhone whereCreatedAt($value)  * @method static IlluminateDatabaseQueryBuilder|AppPhone whereUpdatedAt($value)  * @mixin Eloquent  */ class Phone extends Model {     /**      * @return IlluminateDatabaseEloquentRelationsBelongsTo      */     public function merchant()     {         return $this->belongsTo(Merchant::class, 'merchant_id');     } }  /**  * AppProduct  *  * @property integer $id  * @property string $name  * @property string $short_desc  * @property string $long_desc  * @property float $price  * @property integer $shop_id  * @property CarbonCarbon $created_at  * @property CarbonCarbon $updated_at  * @property-read IlluminateDatabaseEloquentCollection|AppShop[] $shop  * @method static IlluminateDatabaseQueryBuilder|AppProduct whereId($value)  * @method static IlluminateDatabaseQueryBuilder|AppProduct whereName($value)  * @method static IlluminateDatabaseQueryBuilder|AppProduct whereShortDesc($value)  * @method static IlluminateDatabaseQueryBuilder|AppProduct whereLongDesc($value)  * @method static IlluminateDatabaseQueryBuilder|AppProduct wherePrice($value)  * @method static IlluminateDatabaseQueryBuilder|AppProduct whereShopId($value)  * @method static IlluminateDatabaseQueryBuilder|AppProduct whereCreatedAt($value)  * @method static IlluminateDatabaseQueryBuilder|AppProduct whereUpdatedAt($value)  * @mixin Eloquent  */ class Product extends Model {     /**      * @return IlluminateDatabaseEloquentRelationsBelongsTo      */     public function shop()     {         return $this->belongsTo(Shop::class, 'shop_id');     } }  /**  * AppShop  *  * @property integer $id  * @property string $name  * @property string $slug  * @property string $site  * @property integer $merchant_id  * @property CarbonCarbon $created_at  * @property CarbonCarbon $updated_at  * @property-read IlluminateDatabaseEloquentCollection|AppMerchant[] $merchant  * @property-read IlluminateDatabaseEloquentCollection|AppProduct[] $products  * @method static IlluminateDatabaseQueryBuilder|AppShop whereId($value)  * @method static IlluminateDatabaseQueryBuilder|AppShop whereName($value)  * @method static IlluminateDatabaseQueryBuilder|AppShop whereSlug($value)  * @method static IlluminateDatabaseQueryBuilder|AppShop whereSite($value)  * @method static IlluminateDatabaseQueryBuilder|AppShop whereMerchantId($value)  * @method static IlluminateDatabaseQueryBuilder|AppShop whereCreatedAt($value)  * @method static IlluminateDatabaseQueryBuilder|AppShop whereUpdatedAt($value)  * @mixin Eloquent  */ class Shop extends Model {     /**      * @return IlluminateDatabaseEloquentRelationsBelongsTo      */     public function merchant()     {         return $this->belongsTo(Merchant::class, 'merchant_id');     }      /**      * @return IlluminateDatabaseEloquentRelationsHasMany      */     public function products()     {         return $this->hasMany(Product::class, 'shop_id');     } }

別忘了利用下開發三件套輸入指令:

php artisan ide-helper:generate php artisan ide-helper:models php artisan test-factory-helper:generate

表的關系如圖:

詳解Laravel之模型關聯預加載

然后寫Seeder,可以參考Laravel學習筆記之Seeder填充數據小技巧:

php artisan make:seeder MerchantTableSeeder php artisan make:seeder PhoneTableSeeder php artisan make:seeder ShopTableSeeder php artisan make:seeder ProductTableSeeder class MerchantTableSeeder extends Seeder {     /**      * Run the database seeds.      *      * @return void      */     public function run()     {         $faker = FakerFactory::create();         $datas = [];         foreach (range(1, 20) as $key => $value) {             $datas[] = [                 'username'   =>  $faker->userName ,                 'email'      =>  $faker->safeEmail ,                 'first_name' =>  $faker->firstName ,                 'last_name'  =>  $faker->lastName ,                 'created_at' => CarbonCarbon::now()->toDateTimeString(),                 'updated_at' => CarbonCarbon::now()->toDateTimeString()             ];         }          DB::table('merchants')->insert($datas);     } }  class PhoneTableSeeder extends Seeder {     /**      * Run the database seeds.      *      * @return void      */     public function run()     {         $faker        = FakerFactory::create();         $merchant_ids = AppMerchant::lists('id')->toArray();         $datas        = [];         foreach (range(1, 20) as $key => $value) {             $datas[]  = [                 'number'      => $faker->randomNumber() ,                 'merchant_id' => $faker->randomElement($merchant_ids) ,                 'created_at'  => CarbonCarbon::now()->toDateTimeString(),                 'updated_at'  => CarbonCarbon::now()->toDateTimeString()             ];         }          DB::table('phones')->insert($datas);     } }  class ShopTableSeeder extends Seeder {     /**      * Run the database seeds.      *      * @return void      */     public function run()     {         $faker        = FakerFactory::create();         $merchant_ids = AppMerchant::lists('id')->toArray();         $datas        = [];         foreach (range(1, 40) as $key => $value) {             $datas[]  = [                 'name'         =>  $faker->name ,                 'slug'         =>  $faker->slug ,                 'site'         =>  $faker->word ,                 'merchant_id'  =>  $faker->randomElement($merchant_ids) ,                 'created_at'   => CarbonCarbon::now()->toDateTimeString(),                 'updated_at'   => CarbonCarbon::now()->toDateTimeString()             ];         }          DB::table('shops')->insert($datas);     } }  class ProductTableSeeder extends Seeder {     /**      * Run the database seeds.      *      * @return void      */     public function run()     {         $faker    = FakerFactory::create();         $shop_ids = AppShop::lists('id')->toArray();         $datas    = [];         foreach (range(1, 30) as $key => $value) {             $datas[] = [                 'name'              =>  $faker->name ,                 'short_desc'        =>  $faker->text ,                 'long_desc'         =>  $faker->text ,                 'price'             =>  $faker->randomFloat() ,                 'shop_id'           =>  $faker->randomElement($shop_ids) ,                 'created_at'        =>  CarbonCarbon::now()->toDateTimeString() ,                 'updated_at'        =>  CarbonCarbon::now()->toDateTimeString()             ];         }          DB::table('products')->insert($datas);     } }  php artisan db:seed

3.寫個簡單View視圖
(1)用Repository Pattern來組織代碼

//app/Repository namespace AppRepository; interface ShopRepositoryInterface {     public function all(); } //app/Repository/Eloquent namespace AppRepositoryEloquent;  use AppRepositoryShopRepositoryInterface; use AppShop;  class ShopRepository implements ShopRepositoryInterface {     /**      * @var Shop      */     public $shop;     public function __construct(Shop $shop)     {         $this->shop = $shop;     }      public function all()     {         // TODO: Implement all() method.         $shops = $this->shop->all();         return $shops;     } } //app/provider/ShopRepositoryServiceProvider //php artisan make:provider ShopRepositoryServiceProvider /**      * Register the application services.      *      * @return void      */     public function register()     {         $this->app->bind(ShopRepositoryInterface::class, ShopRepository::class);     }      //app/Http/Controllers/ShopController.php class ShopController extends Controller {     /**      * @var ShopRepositoryInterface      */     public $shop;      /**      * ShopController constructor.      * @param ShopRepositoryInterface $shopRepositoryInterface      */     public function __construct(ShopRepositoryInterface $shopRepositoryInterface)     {         $this->shop = $shopRepositoryInterface;     }      public function all()     {         $shops = $this->shop->all();         return view('shop.index', compact('shops'));     } }  //視圖 //resources/views/shop/layout.blade.php <html lang="en"> <head>     <meta charset="utf-8">     <meta http-equiv="X-UA-Compatible" content="IE=edge">     <meta name="viewport" content="width=device-width, initial-scale=1">     <!-- 上述3個meta標簽*必須*放在最前面,任何其他內容都*必須*跟隨其后! -->     <title>Bootstrap Template</title>     <!-- 新 Bootstrap 核心 CSS 文件 -->     <link rel="stylesheet" href="//cdn.bootcss.com/bootstrap/3.3.5/css/bootstrap.min.css">     <style>         html,body{             width: 100%;             height: 100%;         }         *{             margin: 0;             border: 0;         }     </style> </head> <body> <p class="container">     <p class="row">         <p class="col-xs-12 col-md-12">              @yield('content')          </p>     </p> </p>  <!-- jQuery文件。務必在bootstrap.min.js 之前引入 --> <script src="//cdn.bootcss.com/jquery/1.11.3/jquery.min.js"></script> <!-- 最新的 Bootstrap 核心 JavaScript 文件 --> <script src="//cdn.bootcss.com/bootstrap/3.3.5/js/bootstrap.min.js"></script> <script>  </script> </body> </html>  //resources/views/shop/index.blade.php @extends('shop.layout')  @section('content')     <ul class="list-group">         @foreach($shops as $shop)             <li class="list-group-item" style="margin-top: 10px">                 <h1><strong style="color: darkred">Store:</strong>{{$shop->name}}</h1>                 <span><strong style="color: orangered">Member:</strong>{{$shop->merchant->first_name.' '.$shop->merchant->last_name}}</span>                 {{--這里數組取電話號碼--}}                 <span><strong style="color: orangered">Phone:</strong>{{$shop->merchant->phone['number']}}</span>                 <ul class="list-group">                     @foreach($shop->products as $product)                         <li class="list-group-item">                             <h3><strong style="color: red">Name:</strong>{{$product->name}}</h3>                             <h4><strong style="color: red">Desc:</strong>{{$product->short_desc}}</h4>                             <h4><strong style="color: red">Price:</strong>{{$product->price}}</h4>  {{--                            {!! Debugbar::info('products:'.$product->id) !!}--}}                         </li>                     @endforeach                 </ul>             </li>         @endforeach     </ul>  @endsection  //路由 Route::get('/eagerload', 'ShopController@all');

(2)Debugbar查看程序執行數據
詳解Laravel之模型關聯預加載

可以看到,執行了121次query,耗時38.89ms,效率很低,仔細觀察每一個statement就發現這是先掃描shops表,再根據shops中每一個merchant_id去查找merchants表,查找products表也是這樣,又有很多次query,這是N+1查找問題。

預加載查詢

(1)嵌套預加載
Eloquent在通過屬性訪問關聯數據時是延遲加載的,就是只有該關聯數據只有在通過屬性訪問它時才會被加載。在查找上層模型時可以通過預加載關聯數據,避免N+1問題。而且,使用預加載超級簡單。
只需修改一行:

//app/Repository/Eloquent/ShopRepository     public function all()     {         // TODO: Implement all() method. //        $shops = $this->shop->all();         //通過`點`語法嵌套預加載,多種關聯就寫對應的關聯方法         //Shop這個Model里關聯方法是Merchant()和Products(),Merchant Model里關聯方法是Phone()         $shops = $this->shop->with(['merchant.phone', 'products'])->get();         return $shops;     }

不需要修改其他代碼,再看Debugbar里的查詢:
詳解Laravel之模型關聯預加載

It is working!!!

發現:只有4個query,耗時3.58ms,效率提高很多。把原來的N+1這種query改造成了where..in..這種query,效率提高不少。可以用EXPLAIN來查看SQL語句的執行計劃。

(2)預加載條件限制
還可以對預加載進行條件限制,如對products進行預先排序,代碼也很好修改,只需:

//app/Repository/Eloquent/ShopRepository public function all()     {         // TODO: Implement all() method. //        $shops = $this->shop->all(); //        $shops = $this->shop->with(['merchant.phone', 'products'])->get();         $shops = $this->shop->with(['members.phone', 'products'=>function($query){ //            $query->orderBy('price', 'desc');             $query->orderBy('price', 'asc');         }])->get();         return $shops;     }

通過加個限制條件,就等于在預加載products時SQL語句上加個排序。截圖就不截取了。

總結:關聯模型預加載的確是個有意思的功能,效率提高不少。最近都在瞎研究,遇到好玩的東西再分享出來吧,到時見。

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