thinkphp6使用mysql悲观锁解决商品超卖问题的实现

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我是靠谱客的博主忧虑奇迹，这篇文章主要介绍thinkphp6使用mysql悲观锁解决商品超卖问题的实现，现在分享给大家，希望可以做个参考。

悲观锁介绍（百科）：

悲观锁，正如其名，它指的是对数据被外界（包括本系统当前的其他事务，以及来自外部系统的事务处理）修改持保守态度，因此，在整个数据处理过程中，将数据处于锁定状态。悲观锁的实现，往往依靠数据库提供的锁机制（也只有数据库层提供的锁机制才能真正保证数据访问的排他性，否则，即使在本系统中实现了加锁机制，也无法保证外部系统不会修改数据）。

使用场景举例：以MySQL InnoDB为例

商品goods表，假设商品的id为1，购买数量为1，status为1表示上架中，2表示下架。现在用户购买此商品，在不是高并发的情况下处理逻辑是：

查找此商品的信息；
检查商品库存是否大于购买数量；
修改商品库存和销量；

上面这种场景在高并发访问的情况下很可能会出现问题。如果商品库存是100个，高并发的情况下可能会有1000个同时访问，在到达第2步的时候，都会检测通过。这样会出现商品库存是-900个的情况。显然着不满足需求！！！

商品表结构：

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CREATE TABLE `goods` (
  `id` int(11) unsigned NOT NULL AUTO_INCREMENT,
  `name` varchar(100) COLLATE utf8_unicode_ci NOT NULL DEFAULT '',
  `status` tinyint(1) NOT NULL DEFAULT '1',
  `total` int(11) NOT NULL DEFAULT '0',
  `sell` int(11) NOT NULL DEFAULT '100',
  `price` decimal(10,2) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;
 
INSERT INTO `test`.`goods`(`id`, `name`, `status`, `total`, `sell`, `price`) VALUES (1, '商品', 1, 0, 100, 15.00);

订单表结构：

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CREATE TABLE `orders` (
  `id` int(11) unsigned NOT NULL AUTO_INCREMENT,
  `uid` int(11) NOT NULL DEFAULT '0',
  `create_time` datetime NOT NULL,
  `status` tinyint(1) NOT NULL DEFAULT '1',
  `goods_id` int(11) NOT NULL DEFAULT '0',
  `order_no` varchar(200) COLLATE utf8_unicode_ci NOT NULL DEFAULT '',
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;

使用悲观锁处理。

当我们在查询出goods信息后就把当前的数据锁定，直到我们修改完毕后再解锁。那么在这个过程中，因为goods被锁定了，就不会出现有第三者来对其进行修改了。

注：要使用悲观锁，我们必须关闭mysql数据库的自动提交属性，因为MySQL默认使用autocommit模式，也就是说，当你执行一个更新操作后，MySQL会立刻将结果进行提交。thinkphp6中使用事务，手动进行提交回滚。

复制代码

<?php
 
namespace appcontroller;
 
use appBaseController;
use thinkfacadeDb;
 
class Test extends BaseController
{
 
    /**
     * 不加锁
     * @return string|void
     */
    public function test_1()
    {
        $num = 1;
        $goods_id = 1;
        Db::startTrans();
        try {
            $where = [];
            $where['id'] = $goods_id;
            $where['status'] = 1;
            $goods_info = Db::table('goods')->where($where)->find();
            if (empty($goods_info)) {
                return '商品不存在';
            }
            $total = $goods_info['total'];
            $sell = $goods_info['sell'];
            if ($total < $num) {
                return '库存不足';
            }
            $data['total'] = $total-$num;
            $data['sell'] = $sell+$num;
            $res = Db::table('goods')->where(['id'=>$goods_id])->update($data);
            $order_data = [];
            $order_data['uid'] = rand(1000,9999);
            $order_data['status'] = 1;
            $order_data['create_time'] = date('Y-m-d H:i:s');
            $order_data['goods_id'] = $goods_id;
            $order_data['order_no'] = date('YmdHis').rand(1000,10000);
            $order_res = Db::table('orders')->insert($order_data);
            Db::commit();
        } catch (Exception $e) {
            // 回滚事务
            Db::rollback();
            echo $e->getMessage();
            exit('rollback');
        }
        echo '请求成功';
    }
 
    /**
     * 加锁--悲观锁
     * @return string|void
     */
    public function test_2()
    {
        $num = 1;
        $goods_id = 1;
        Db::startTrans();
        try {
            $where = [];
            $where['id'] = $goods_id;
            $where['status'] = 1;
            $goods_info = Db::table('goods')->lock(true)->where($where)->find();
            if (empty($goods_info)) {
                return '商品不存在';
            }
            $total = $goods_info['total'];
            $sell = $goods_info['sell'];
            if ($total < $num) {
                return '库存不足';
            }
            $data['total'] = $total-$num;
            $data['sell'] = $sell+$num;
            $res = Db::table('goods')->where(['id'=>$goods_id])->update($data);
            $order_data = [];
            $order_data['uid'] = rand(1000,9999);
            $order_data['status'] = 1;
            $order_data['goods_id'] = $goods_id;
            $order_data['order_no'] = date('YmdHis').rand(1000,10000);
            $order_data['create_time'] = date('Y-m-d H:i:s');
            $order_res = Db::table('orders')->insert($order_data);
            Db::commit();
        } catch (Exception $e) {
            // 回滚事务
            Db::rollback();
            echo $e->getMessage();
            exit('rollback');
 
        }
        echo '请求成功';
    }
 
}

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<?php
 
namespace appcontroller;
 
use appBaseController;
use thinkfacadeDb;
 
class Test extends BaseController
{
 
    /**
     * 不加锁
     * @return string|void
     */
    public function test_1()
    {
        $num = 1;
        $goods_id = 1;
        Db::startTrans();
        try {
            $where = [];
            $where['id'] = $goods_id;
            $where['status'] = 1;
            $goods_info = Db::table('goods')->where($where)->find();
            if (empty($goods_info)) {
                return '商品不存在';
            }
            $total = $goods_info['total'];
            $sell = $goods_info['sell'];
            if ($total < $num) {
                return '库存不足';
            }
            $data['total'] = $total-$num;
            $data['sell'] = $sell+$num;
            $res = Db::table('goods')->where(['id'=>$goods_id])->update($data);
            $order_data = [];
            $order_data['uid'] = rand(1000,9999);
            $order_data['status'] = 1;
            $order_data['create_time'] = date('Y-m-d H:i:s');
            $order_data['goods_id'] = $goods_id;
            $order_data['order_no'] = date('YmdHis').rand(1000,10000);
            $order_res = Db::table('orders')->insert($order_data);
            Db::commit();
        } catch (Exception $e) {
            // 回滚事务
            Db::rollback();
            echo $e->getMessage();
            exit('rollback');
        }
        echo '请求成功';
    }
 
    /**
     * 加锁--悲观锁
     * @return string|void
     */
    public function test_2()
    {
        $num = 1;
        $goods_id = 1;
        Db::startTrans();
        try {
            $where = [];
            $where['id'] = $goods_id;
            $where['status'] = 1;
            $goods_info = Db::table('goods')->lock(true)->where($where)->find();
            if (empty($goods_info)) {
                return '商品不存在';
            }
            $total = $goods_info['total'];
            $sell = $goods_info['sell'];
            if ($total < $num) {
                return '库存不足';
            }
            $data['total'] = $total-$num;
            $data['sell'] = $sell+$num;
            $res = Db::table('goods')->where(['id'=>$goods_id])->update($data);
            $order_data = [];
            $order_data['uid'] = rand(1000,9999);
            $order_data['status'] = 1;
            $order_data['goods_id'] = $goods_id;
            $order_data['order_no'] = date('YmdHis').rand(1000,10000);
            $order_data['create_time'] = date('Y-m-d H:i:s');
            $order_res = Db::table('orders')->insert($order_data);
            Db::commit();
        } catch (Exception $e) {
            // 回滚事务
            Db::rollback();
            echo $e->getMessage();
            exit('rollback');
 
        }
        echo '请求成功';
    }
 
}