解决PHP与MySQL并发更新中的竞态条件：确保数据一致性的策略

use App\Models\Card;
use Illuminate\Http\Request;

public function setAsDefault(Request $request, $id)
{
  // 步骤1: 将用户所有卡片设为非默认
  Card::where('user_id', $request->user()->id)->update(['is_default' => false]);

  // 步骤2: 将指定卡片设为默认
  Card::where([
    'id' => $id,
    'user_id' => $request->user()->id
  ])->update(['is_default' => true]);

  return ['status' => true];
}

use Illuminate\Support\Facades\DB;
use App\Models\Card;
use Illuminate\Http\Request;

public function setAsDefault(Request $request, $id)
{
    DB::transaction(function () use ($request, $id) {
        // 将用户所有卡片设为非默认
        Card::where('user_id', $request->user()->id)
            ->update(['is_default' => false]);

        // 将指定卡片设为默认
        Card::where([
            'id' => $id,
            'user_id' => $request->user()->id
        ])->update(['is_default' => true]);
    });

    return ['status' => true];
}

use Illuminate\Support\Facades\DB;
use App\Models\Card;
use Illuminate\Http\Request;

public function setAsDefaultWithLock(Request $request, $id)
{
    DB::transaction(function () use ($request, $id) {
        // 在更新前，先锁定该用户的所有卡片记录
        // 确保在当前事务完成前，没有其他事务能修改这些卡片
        Card::where('user_id', $request->user()->id)
            ->lockForUpdate() // 对查询结果加排他锁
            ->get(); // 执行查询以应用锁

        // 执行更新操作
        Card::where('user_id', $request->user()->id)
            ->update(['is_default' => false]);

        Card::where([
            'id' => $id,
            'user_id' => $request->user()->id
        ])->update(['is_default' => true]);
    });

    return ['status' => true];
}

// routes/api.php 或 routes/web.php
use Illuminate\Cache\RateLimiting\Limit;
use Illuminate\Support\Facades\RateLimiter;

RateLimiter::for('set-default-card', function (Request $request) {
    return Limit::perMinute(5)->by($request->user()->id); // 每个用户每分钟最多5次
});

Route::patch('/cards/{id}/default', [CardController::class, 'setAsDefault'])
    ->middleware(['throttle:set-default-card']);