Laravel 5.5 - 如何查询带有 created_at 时间戳的关注者的通知？

Question

用户可以是追随者 and/or 领导者。这里 userA 和 userB（都是领导者）在不同时间被 userC（追随者）跟随（请参阅下面的 followers table created_at 时间戳）。

为了说明问题，我先排一下模板：

userX action (year) // template to understand issue below

userC followed userA (2016)
userA added postA/notification (2017)
userC should get notification in feed, since they followed userA a year BEFORE their post

userB added postB/notification (2018)
userC followed userB (2019)
userC should NOT get notification in feed, since they followed userB a year AFTER their post

为此，我尝试了这个查询，但它无法正常工作：

$user = App\User::find(3); // follower
$leaders = $user->leaders()
                ->with(['leaderNotifications'=>function($query){
              $query->where('notifications.created_at','>','followers.created_at');
                }])
                ->get();

我认为这个问题与 created_at 没有被正确查询有关。这是在本地查看的确切设置：

1) DB table name/data

users

followers

notifications

2) 型号

// User
<?php
namespace App;

use Illuminate\Notifications\Notifiable;
use Illuminate\Foundation\Auth\User as Authenticatable;
use Illuminate\Notifications\DatabaseNotification;
use Illuminate\Notifications\DatabaseNotificationCollection;

class User extends Authenticatable {
    use Notifiable;

    // Pivot Table
    public function leaders() {
      return $this->belongsToMany('App\User', ‘followers’, 'follower_id', 'leader_id')
                  ->withPivot('created_at'); // need timestamp to compare against notification timestamp
    }

    public function leaderNotifications() {
        return $this->hasMany(DatabaseNotification::class, 'leader_id')
                    ->orderBy('created_at', 'desc');
    }
}

我正在尝试获取当前关注者 userC 的正确通知，这意味着只有他们关注领导者之后的新通知，而不是领导者的旧通知 before 他们被当前用户关注了。还值得注意的是，最终查询应该能够一次 paginate->(20) 这些通知，因为它将用一百万行进行测试，所以我们需要确保它是 efficient/scalable 并且可以分页。这个问题的 efficient/scalable 查询是什么？

Answer 1

1) For raw query in Laravel you should using whereRaw.

2) When using with(), Laravel get data in two query , first get result of parent query and then using result for getting with() , If you want to use pivot columns of first query in with closure,you can join.

试试这个：

$user = App\User::find(3); // follower
$leaders = $user
          ->leaders()
          ->with(['leaderNotifications'=>function($query) use ($user){
              $query->whereRaw('notifications.created_at > followers.created_at')
                    ->join('followers','followers.leader_id','=','notifications.leader_id')
                    ->where('followers.follower_id',$user['id']);
                 }])
            ->get();

Answer 2

以下是我的解决方法以防对其他人有帮助：

$user = App\User::find(3); // follower
$leaders = DB::table('notifications')
             ->join('followers','followers.leader_id','=','notifications.leader_id')
             ->where('followers.follower_id', $user->id)
             ->whereRaw('notifications.created_at > followers.created_at')
             ->paginate(20);

无需预先加载或使其更加复杂。只需一个简单的 DB 查询即可处理！

Laravel 5.5 - 如何查询带有 created_at 时间戳的关注者的通知？

Laravel 5.5 - How to query notifications for follower with created_at timestamp?

eager-loading

laravel

eloquent

laravel-5

laravel-5.5